Polymerisation process and polymer product

ABSTRACT

A method of polymerising monomer to form polymer at the surface of particulate material, said method comprising: providing a dispersion of said particulate material in a continuous liquid phase, said dispersion comprising a RAFT agent as a stabiliser for said particulate material, and said continuous liquid phase comprising one or more ethylenically unsaturated monomers; and polymerising said one or more ethylenically unsaturated monomers under the control of said RAFT agent to thereby form polymer at the surface of said particulate material.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a divisional of 371 application Ser. No. 11/664,592,filed Apr. 4, 2008, which is a National Stage entry of InternationalApplication No. PCT/AU2005/001512, filed Oct. 4, 2005, which claimsbenefit of priority to Australian Patent Application Nos. 2004905729 and2005903366, filed Oct. 4, 2004 and Jun. 24, 2005, respectively. Theentire specification, claims, and drawings of which are incorporatedherewith by reference.

FIELD OF THE INVENTION

The present invention relates to a method of polymerising monomer toform polymer at the surface of particulate material, to polymerencapsulated particulate material and to products comprising the polymerencapsulated particulate material. The polymer encapsulated particulatematerial is particularly suited for use in coating formulations, and itwill therefore be convenient to describe the invention with an emphasistoward this application. However, it is to be understood that thepolymer encapsulated particulate material may be used in variousapplications.

BACKGROUND OF THE INVENTION

Deposition of polymer at the surface of particulate materials can affordpolymer/particulate material composites that may be used in variousapplications. For example, polymer may be deposited to coat andencapsulate the particulate material. In this case, the polymer coatingcould be used to protect the particulate material from an externalenvironment, to effect the controlled release of the particulatematerial to an external environment, and/or to alter the surfacecharacteristics that the particulate material presents to an externalenvironment. As a case in point, polymer encapsulated pesticide,herbicide or pharmaceutical particulate materials may be used to providecontrolled release products.

Alternatively, polymer encapsulated pigment particulate material mightbe used to enhance certain characteristics of paint formulations.

For the efficiency and reliability of products comprising suchpolymer/particulate material composites, it is generally desirable thatpolymer is deposited at the surface of the particulate material in arelatively controlled, even and reproducible manner. Where theparticulate material is encapsulated in and dispersed throughout a bulkpolymeric matrix, it will also be generally desirable that theparticulate material is uniformly dispersed throughout that matrix.

To date, a common approach to encapsulate particulate materials withpolymer has involved dispersing the particulate material into a liquidmedium comprising a preformed polymer. The liquid medium may be formedby dissolving the polymer in a solvent, or by simply melting thepolymer. Alternatively, the particulate material might be dispersed inmonomer which is then polymerised to form the polymer. However, theability to successfully apply such methodologies is often highly polymerand/or particulate material dependent. Furthermore, dispersing agents(i.e. agents with surface activity such as surfactants) often need to beused to facilitate the dispersion of the particulate material in thecoating medium. The use of conventional dispersing agents in this mannercan be detrimental to the final products in which thepolymer/particulate material composites are employed. In particular,conventional dispersing agents are prone to migrate and localise andthereby undesirably alter the wetting characteristics of the product.

A further problem associated with conventional techniques for depositingpolymer to coat and encapsulate particulate materials is that theytypically afford little if no control over being able to reproduciblycoat the particulate material with a relatively uniform layer of polymerat a variety of thicknesses.

As an alternative to coating particles with preformed polymer, attemptshave been made to use conventional free radical polymerisation processesto form polymer at the surface of particulate material. However, suchattempts have been generally unsuccessful. In particular, processesemploying conventional free radical polymerisation techniques topolymerise monomer at the surface of particulate materials are generallynot very controllable and have a tendency to produce pimples of, oruneven, polymer at the surface of the particles rather than a uniformpolymer coating.

Numerous other methods for depositing polymer at the surface ofparticulate materials have been reported. However, such methods havegenerally offered little in the way of improved control over the polymerdeposition and/or are commercially non-viable.

Accordingly, there remains a need for a commercially viable method fordepositing polymer in a controllable manner at the surface ofparticulate materials. Such a method will preferably be robust,efficient and capable of being applied to a broad range of polymers andparticle types and sizes.

SUMMARY OF THE INVENTION

The present invention provides a method of polymerising monomer to formpolymer at the surface of particulate material, said method comprising:

providing a dispersion of said particulate material in a continuousliquid phase, said dispersion comprising a RAFT agent as a stabiliserfor said particulate material, and said continuous liquid phasecomprising one or more ethylenically unsaturated monomers; and

polymerising said one or more ethylenically unsaturated monomers underthe control of said RAFT agent to thereby form polymer at the surface ofsaid particulate material.

In essence, the method of the invention provides a unique interfacialpolymerisation technique that enables polymer to be formed at thesurface of particulate materials in a substantially controllable andreproducible manner. The method enables a diverse array of polymers tobe formed at the surface of an equally diverse array of particulatematerials. Provided that the particulate material can be dispersed inthe continuous liquid phase, the particles can be of any shape or size.

Through the control afforded by the method, polymer may be formed at thesurface of the particulate material in a substantially even fashion andcan be provided at tailored thicknesses. Such control advantageouslyenables the particulate material to be encapsulated by a desiredthickness of polymer to provide for a dispersion of polymer encapsulatedparticulate material in a liquid. Alternatively, where suchpolymerisation is allowed to continue and sufficient polymer mass isformed, polymer which encapsulates the particulate material may coalesceto provide for a polymer mass having the particulate material dispersedsubstantially uniformly therethrough. In this case, it may be that thecontinuous liquid phase consists essentially of the monomer to bepolymerised.

In one aspect the present invention provides polymer encapsulatedparticulate material that is 100 microns or less in size, saidparticulate material being encapsulated in a substantially uniform andcontinuous coating of a polymer which has at least in part been formedunder the control of a RAFT agent.

The present invention also provides polymer encapsulated particulatematerial that is 100 microns or less in size, wherein the encapsulatingpolymer has at least in part been formed under the control of a RAFTagent, and wherein the particulate material is substantially uniformlydispersed throughout the encapsulating polymer.

Further aspects of the invention appear below in the detaileddescription of the invention.

BRIEF DESCRIPTION OF THE DRAWINGS

Preferred embodiments of the invention will now be illustrated by way ofExample only with reference to the accompanying drawings in which:

FIG. 1 illustrates polymer encapsulated TiO₂ pigment prepared inaccordance with the invention;

FIGS. 2 and 3 illustrate polymer encapsulated phthalocyanine bluepigment prepared in accordance with the invention.

FIG. 4 shows scattering and absorption coefficients over a range ofwavelengths in the visible region as described in Example 13.

DETAILED DESCRIPTION OF THE INVENTION

In accordance with certain aspects of the invention, the RAFT agentfunctions as a stabiliser for the dispersed particulate material. Byfunctioning as “a stabiliser”, the RAFT agent serves to prevent, or atleast minimise, coalescence or aggregation of the dispersed particulatematerial. As a stabiliser, the RAFT agent may prevent, or at leastminimise, coalescence or aggregation of the particulate material throughwell known pathways such as steric and/or electrostatic repulsion. Toprovide the ability to function as a stabiliser, the RAFT agentcomprises a moiety that can provide for the requisite steric and/orelectrostatic repulsion.

A feature of certain aspects of the invention is that the one or moreethylenically unsaturated monomers are polymerised under the control ofthe RAFT agent. By being polymerised “under the control” of the RAFTagent is meant that the monomers are polymerised via a ReversibleAddition-Fragmentation chain Transfer (RAFT) mechanism to form polymer.

RAFT polymerisation of ethylenically unsaturated monomers is describedin WO 98/01478, and in effect is a radical polymerisation technique thatenables polymers to be prepared having a well defined moleculararchitecture and low polydispersity. The technique employs a RAFT agentof the general formula (1):

which has been proposed to react with a propagating radical (P_(n)*) inaccordance with Scheme 1.

The effectiveness of the RAFT agent (1) is believed to depend on acomplex array of rate constants. In particular, the formation of polymeraccording to scheme 1 is believed to be reliant upon equilibria thatrequire high rate constants for the addition of propagating radicals toagent (1) and the fragmentation of intermediate radicals (2) and (3),relative to the rate constant for propagation.

The rate constants associated with RAFT polymerisation are believed tobe influenced by a complex interplay between stability, steric andpolarity effects in the substrate, the radicals and the products formed.The polymerisation of specific monomers and combinations of monomerswill introduce different factors and structural preferences for theagent (1). The interplay of factors for a particular system have beenlargely rationalised on the basis of the results obtained. A cleardefinition of all factors that influence polymerisation for anyparticular system is yet to be fully understood

As used herein, the phrase “RAFT polymer” is intended to denote apolymer that is formed through one or more ethylenically unsaturatedmonomers being polymerised under the control of a RAFT agent.

In accordance with the method of the invention, monomers are polymerisedto form polymer at the surface of the particulate material. By polymerbeing formed “at the surface” is meant that polymer forms on orimmediately adjacent (i.e. in the direction of the continuous liquidphase) the outermost surface of the particulate material. In otherwords, polymer forms at the interface between the particulate materialand the continuous liquid phase such that it can coat the particulatematerial. Polymer will generally be formed so as to fully coat orencapsulate the particulate material.

As used herein, the phrase “particulate material” is intended to embraceany material that is capable of being dispersed throughout thecontinuous liquid phase, be it a solid, semi-solid or liquid. By theparticulate material being “dispersed” throughout the continuous phase,it in effect forms a discontinuous phase within the continuous liquidphase. Provided that it can be dispersed throughout the continuousliquid phase, the particulate material may take any shape or size.However, it is recognised that particulate materials having a highaspect ratio, for example those having a flat lamellar or needle shape,may prove more difficult to uniformly coat with polymer than particulatematerial having a low aspect ratio.

The dispersed particulate material may be in the form of primaryparticles, or in the form of an aggregation of primary particles. Themethod of the invention has advantageously been found to be particularlyeffective at forming polymer at the surface of primary particles.

Given that polymer is formed at the surface of the particulate material,it will be appreciated that the particulate material per se should besubstantially free of monomer that may be polymerised under the controlof the RAFT agent. If the particulate material were to contain monomer,for example as in a liquid particle comprising monomer, polymer islikely to form internally or within the particulate material.

Those skilled in the art will appreciate that as the size of particulatematerials decrease, the degree of difficulty in being able to depositpolymer in a controllable manner at the surface of the materialsincreases. The unique interfacial polymerisation afforded by the methodof the invention advantageously enables polymer to be formed in acontrolled manner with relative ease at the surface of both small andlarge particles alike, be they primary particles or aggregates thereof.

Accordingly, the particulate material may be of any type, shape or sizeprovided that it can be dispersed throughout the continuous liquidphase. Preferably, the largest dimension of the particulate material isno greater than 10 microns, more preferably no greater than 2 microns.The method of the invention has been found to be particularly effectiveat forming polymer at the surface of sub-micron particles, for exampleless than 0.5 microns, even less than 0.25 microns.

Suitable substances from which the particulate material may be formedinclude, but are not limited to, pigments in general, inorganic materialsuch as titanium dioxide, zinc oxide, calcium carbonate, iron oxide,silicon dioxide, barium sulfate, carbon black, organic pigments such asphthalocyanine blue, phthalocyanine green, quinacridone anddibromananthrone, magnetic materials such as y-iron oxide, waxes,bioactive agents such as pesticides, herbicides, fungicides andpharmaceuticals, water, and combinations thereof.

Preferably, the particulate material is a solid (i.e. in solid form atthe temperature which the method of the invention is performed).

It is generally preferred that the particulate material that is to beencapsulated by polymer is substantially inert to the reactionconditions under which the RAFT polymerisation process is conducted.

In further describing the nature of, and the interaction between, thecontinuous liquid phase and the dispersed particulate material it can beconvenient to refer to their relative solubility and/or polarity. Forexample, in order to provide a continuous liquid phase and a dispersedliquid particulate material, the liquids will typically havesufficiently different polarities to render them substantiallyimmiscible. In other words, one liquid will be sufficiently hydrophilicand the other sufficiently hydrophobic so that they form a polyphasicsystem. In contrast, to provide a continuous liquid phase and adispersed solid particulate material the solid need only be insoluble inthe liquid phase, with the polarity that the solid particulate materialpresents to the liquid phase, and vice versa, generally being irrelevantto forming the dispersion.

From the forgoing, those skilled in the art will appreciate that theterms “hydrophilic” and “hydrophobic” used herein are not intended todefine absolute qualities of a particular substance but rather to be anindicator of a favourable or unfavourable interactions (i.e. attractiveor repulsive interactions). In other words, the terms “hydrophilic” and“hydrophobic” are used herein as primary indicators to definecharacteristics such as like attracting like and unlike repellingunlike.

As a convenient point of reference only, a person skilled in the artmight consider a “hydrophilic” liquid to have a solubility in water ofat least 5 g/L at 25° C., and a “hydrophobic” liquid to have asolubility in water of less than 5 g/L at 25° C. In terms of a solid,the terms “hydrophilic” and “hydrophobic” might be considered by aperson skilled in the art to be a reference to a solid which could bewetted by (i.e. does not repel) a hydrophilic and hydrophobic liquid,respectively.

In practical terms, the continuous liquid phase in effect functions as areaction medium in which the one or more ethylenically unsaturatedmonomers are polymerised to form polymer at the surface of theparticulate material. The monomer may be present in the continuousliquid phase as a separate liquid phase, it may be fully soluble in thecontinuous liquid phase, or the continuous liquid phase may itselfconsist essentially of the monomer.

Where the continuous liquid phase does not consist essentially of theone or more ethylenically unsaturated monomers, the method of theinvention may be conveniently used to prepare a dispersion of polymerencapsulated particles in a liquid. For example, where the continuousliquid phase comprises water and the particulate material is titaniumdioxide, the method of the invention may be used to prepare an aqueousdispersion of polymer encapsulated titanium dioxide particles.

The moiety of the RAFT agent that functions to stabilise the particulatematerial in the continuous liquid phase can also advantageously functionto stabilise a liquid dispersed polymer encapsulated particulatematerial formed by the method of the invention. Accordingly, noadditional dispersant to disperse the polymer encapsulated particulatematerial in the liquid is required.

By being “encapsulated” is meant that the polymer substantiallysurrounds the entire particulate material. The polymer may, however,exhibit a degree of porosity (i.e. have some holes or voids in it).

In a preferred embodiment the invention provides a method of preparing adispersion of polymer encapsulated particulate material in a liquid,said method comprising:

providing a dispersion of particulate material in a continuous liquidphase, said dispersion comprising a RAFT agent as a stabiliser for saidparticulate material, and said continuous liquid phase comprising one ormore ethylenically unsaturated monomers; and

polymerising said one or more ethylenically unsaturated monomers underthe control of said RAFT agent to form polymer at the surface of saidparticulate material, thereby providing said dispersion of polymerencapsulated particulate material in a liquid.

Preferably, the continuous liquid phase is water and the method producesan aqueous dispersion of polymer encapsulated particulate material.

In accordance with this preferred embodiment, the particulate materialencapsulated by the polymer may be a primary particle or an aggregatethereof. The polymer coating which encapsulates the particles willgenerally be substantially uniform around the entire particle. Providedthe polymer encapsulated particulate material can remain dispersed,encapsulated particles of any size can be prepared using thismethodology. The methodology can also be used to prepare theaforementioned polymer encapsulated particulate material that is 100microns or less in size, wherein the particulate material isencapsulated in a substantially uniform and continuous coating of apolymer. Preferably, such novel polymer encapsulated particulatematerial is 70 microns or less, more preferably 40 microns or less, mostpreferably 5 microns or less in size. The size of the polymerencapsulated particulate material may also be in the sub-micron range,for example from 0.01 to 1 micron. For the avoidance of any doubt,reference to the “size” of the polymer encapsulated particulatematerials in this case is that of the largest dimension provided by thecombination of the polymer coating and the particulate material.

By the particulate material being encapsulated in a “substantiallyuniform and continuous coating” is meant that the coating does notpresent in an irregular manner around the particulate material and thatthe coating is substantially free of holes or voids. To achieve theseproperties, the thickness of the polymer surrounding the particulatematerial will generally be relatively constant. However, it may be thatthe thickness of the encapsulating polymer can vary gradually around theperimeter of the particulate material. For example, the particulatematerial may not be located at the precise centre of a spherical polymercoating. An assessment of the uniformity and continuity of the coatingcan generally be made visually, for example by Transmission ElectronMicroscopy (TEM).

The thickness of the polymer coating which encapsulates the particulatematerial is preferably at least 2 nanometers, more preferably at least 5nanometers, most preferably at least 10 nanometers, still morepreferably at least 20 nanometers. There is no particular limit as tothe thickness of polymer that can encapsulate the particulate material,with the ultimate thickness generally being dictated by the intendedapplication for the encapsulated particles.

Where the continuous liquid phase consists essentially of the one ormore ethylenically unsaturated monomers, polymerisation of the monomerscan result in the continuous liquid phase ultimately forming a polymericmatrix around all of the dispersed particles to thereby form a polymermass having the particles dispersed therethrough. By the particles beinginitially dispersed in essentially monomer, and the monomer beingpolymerised at the surface of the dispersed particulate material, themethod of the invention can in this case advantageously provide apolymer having the particulate material substantially uniformlydispersed therethrough.

In another preferred embodiment the invention provides a method ofpreparing a polymer having particulate material dispersed therethrough,said method comprising:

providing a dispersion of said particulate material in a continuousliquid phase, said dispersion comprising a RAFT agent as a stabiliserfor said particulate material, and said continuous liquid phaseconsisting essentially of one or more ethylenically unsaturatedmonomers; and

polymerising said one or more ethylenically unsaturated monomers underthe control of said RAFT agent to form polymer at the surface of saidparticulate material, thereby providing polymer having the particulatematerial dispersed therethrough.

By the expression “consisting essentially of” one or more ethylenicallyunsaturated monomers is meant that that the continuous liquid phase mayinclude additional ingredients, but only if the additional ingredientsdo not materially alter the basic and novel characteristics of themethod. By way of example only, a continuous liquid phase consistingessentially of one or more ethylenically unsaturated monomers might beone which is based on at least 90 weight percent monomer, preferably atleast 95 weight percent monomer.

Where the continuous liquid phase consists essentially of the one ormore ethylenically unsaturated monomers, it may be desirable toterminate polymerisation of the monomer prior to it all being convertedinto polymer. In this case, such a method could provide a dispersion ofpolymer encapsulated particulate material in the remainingnon-polymerised one or more ethylenically unsaturated monomers.

As a variation on the method of the invention where the continuousliquid phase consists essentially of the one or more ethylenicallyunsaturated monomers, it may be desirable to disperse this continuousliquid phase, which itself has the particulate material dispersedtherethrough, in a further or second continuous liquid phase to providewhat might best be described as a double emulsion. For example, theparticulate material might be dispersed in a continuous liquid phasewhich consists essentially of hydrophobic monomer, this continuousliquid phase could then be dispersed in water. Thus in this context, thefirst mentioned continuous liquid phase (i.e. that which consistsessentially of monomer) may be considered continuous relative toparticulate material dispersed therethrough, and the second mentionedcontinuous liquid phase may be considered continuous relative to thefirst continuous liquid phase dispersed therethrough. By performing themethod in this manner, the monomer may be polymerised to form adispersion of polymer particles which advantageously comprise theparticulate material substantially uniformly dispersed therethrough. Thesize of such polymer particles may be conveniently controlled throughvariation of the droplet size of the dispersed continuous liquid phasecomprising the dispersed particulate material using techniques wellknown in the art.

Preferably, the second continuous phase is an aqueous phase.

In the “double emulsion” method mentioned above, the RAFT agentfunctions as a stabiliser for the particulate material to prevent, or atleast minimise, coalescence or aggregation of the dispersed particulatematerial in the continuous liquid phase which consists essentially ofmonomer. The resulting polymer encapsulated particulate material cantherefore be advantageously substantially free of additional dispersantfor the particulate material. It will be appreciated by those skilled inthe art that a surface active stabiliser will also typically be requiredto prevent, or at least minimise, coalescence or aggregation of thedispersed aforementioned first continuous liquid phase in the secondcontinuous liquid phase. In this case, it is preferred that the firstcontinuous liquid phase is stabilised in the second continuous liquidphase by a colloid stabiliser. Suitable colloid stabilisers include, butare not limited to, cellulosic colloids such as hydroxy ethyl celluloseor polyvinyl alcohol.

In accordance with the “double emulsion” method described above, theparticulate material dispersed throughout the resultant polymer particlemay be a primary particle or an aggregate thereof. Advantageously, theparticulate material will be substantially uniformly dispersedthroughout the polymer particle. Provided the polymer encapsulatedparticulate material can remain dispersed, encapsulated particles of anysize can be prepared using this methodology. The methodology can also beused to prepare the aforementioned polymer encapsulated particulatematerial that is 100 microns or less in size, wherein the particulatematerial is dispersed substantially uniformly throughout the polymer.Preferably, such novel polymer encapsulated particulate material is 70microns or less, more preferably 40 microns or less, most preferably 5microns or less in size. The size of the polymer encapsulated materialmay also be in the sub-micron range, for example from 0.01 to 1 micron,preferably from 0.5 to 1 micron. For the avoidance of any doubt,reference to the size of the polymer encapsulated particulate materialin this case is that of the largest dimension provided by thecombination the polymer and the particulate material dispersedtherethrough.

By the RAFT agent facilitating dispersal of the particulate materialthroughout the continuous monomer phase and therefore the resultingencapsulating polymer, the polymer encapsulated particulate material canbe formed substantially free of additional dispersant.

By the particulate material being dispersed “substantially uniformly”throughout the polymer is meant that the particulate material is notlocalised or agglomerated within the encapsulating polymer. For example,the particulate material should not be concentrated at the centre orperimeter of the encapsulating polymer An assessment of the dispersedstate of the particulate material can generally be made visually, forexample by Transmission Electron Microscopy (TEM).

By being “substantially free of additional dispersant” is meant thatother than the RAFT agent the polymer encapsulated particulate materialcomprises less than 30 wt. %, preferably less than 10 wt. %, morepreferably less than 5 wt. %, most preferably no other dispersant thatis used to disperse the particulate material in the continuous liquidphase, relative to the total amount of dispersant present (i.e.inclusive of the RAFT agent which acts as a stabiliser).

Although the particulate material dispersed throughout the continuousliquid phase is stabilised by the RAFT agent, the particulate materialmay also be stabilised by other stabilisers such as conventionalsurfactants or any other surface active agent. Those skilled in the artwill appreciate the range of surfactants suitable for this purpose.Nevertheless, to avoid certain disadvantages of using conventionalsurfactants it is preferred that the particulate material is stabilisedonly by the RAFT agent. In particular, conventional surfactants are notgenerally capable of being anchored to the resulting polymer/particlecomposite and are therefore prone to migrate from their stabilisationsite. Products formed using polymer/particle composites that compriseconventional surfactant may therefore be adversely effected as a resultof the surfactant migrating and localising in pockets. For example, thewater repellency of the product may be compromised.

RAFT agent used in accordance with the invention not only functions as astabiliser but also plays an active role in forming polymer at thesurface of the particulate material. By virtue of this polymerisationrole, the RAFT agent is inherently covalently bound to the polymer thatis formed and is therefore prevented from migrating. Where aconventional surfactant is used in the method of the invention, thestabilising function of the RAFT agent effectively reduces the amount ofconventional surfactant required and thereby provides a means to atleast minimise the negative effects of using such surfactant.

As used herein, the expressions “polymer/particulate material composite”and “polymer/particle composite” are intended to denote a product formedthrough the deposition of polymer at the surface of particulatematerial.

To function as a stabiliser, the RAFT agent used in accordance with theinvention will generally be physically associated in some way with theoutermost surface of the particulate material. Preferably, the physicalassociation between the RAFT agent and the particulate material will beby way of the RAFT agent being adsorbed onto the outermost surface ofthe particulate material. By having an ability to be adsorbed onto theoutermost surface of the particulate material, it will be appreciatedthat the RAFT agent will exhibit surface activity, or in other words itwill be surface active. An adsorbed RAFT agent can exhibit a degree oflability and is therefore less prone to become enveloped by polymerformed at the surface of the particle. In other words, an adsorbed RAFTagent can have the ability to move freely away from the surface of theparticulate material with the polymer that is being formed.

A surface active RAFT agent used in accordance with the invention willhave a structure that enables it to (a) be preferentially adsorbed ontothe outermost surface of the particulate material rather than besolvated by and in the continuous liquid phase, (b) function as astabiliser for the particulate material, and (c) control polymerisationof the one or more ethylenically unsaturated monomers. Further detailson the structural characteristics of such surface active RAFT agents arediscussed below.

RAFT agents suitable for use in the present invention include those ofgeneral formula (4):

where each X is independently a polymerised residue of an ethylenicallyunsaturated monomer, n is an integer ranging from 0 to 100, preferablyfrom 0 to 60, most preferably from 0 to 30, R¹ is an organic groupoptionally substituted with one or more hydrophilic groups and Z is anygroup that can promote sufficient reactivity of the thiocarbonyl grouptowards radical addition while not slowing the rate of fragmentation tothe extent that there is unacceptable retardation of polymerisation.Preferred R¹ groups include C₁-C₆ alkyl, C₁-C₆ alkoxy aryl orheteroaryl, each of which is substituted with one or more hydrophilicgroups selected from —CO₂H, —CO₂RN, —SO₃H, —OSO₃H, —SORN, —SO₂RN,—OP(OH)₂, —P(OH)₂, —PO(OH)₂, —OH, —ORN, —(OCH₂—CHR)_(w)—OH, —CONH₂,CONHR′, CONR′R″, —NR′R″, —N⁺R′R″R″′, where R is selected from C₁-C₆alkyl, w is 1 to 10, R′, R″ and R″′ are independently selected fromalkyl and aryl which are optionally substituted with one or morehydrophilic substituents selected from —CO₂H, —SO₃H, —OSO₃H, —OH,—(COCH₂CHR)_(w)—OH, —CONH₂, —SOR and SO₂R, and salts thereof, R and ware as defined above. Particularly preferred R¹ groups include, but arenot limited to, —CH(CH₃)CO₂H, —CH(CO₂H)CH₂CO₂H, —C(CH₃)₂CO₂H. PreferredZ groups include, optionally substituted alkoxy, optionally substitutedaryloxy, optionally substituted alkyl, optionally substituted aryl,optionally substituted heterocyclyl, optionally substituted arylalkyl,optionally substituted alkylthio, optionally substituted arylalkylthio,dialkoxy- or diaryloxy-phosphinyl [—P(═O)OR² ₂], dialkyl- ordiaryl-phosphinyl [—P(═O)R² ₂], optionally substituted acylamino,optionally substituted acylimino, optionally substituted amino,R¹—(X)_(n)—S— and a polymer chain formed by any mechanism, for examplepolyalkylene oxide polymers such as water soluble polyethylene glycol orpolypropylene glycol, and alkyl end capped derivatives thereof, whereR¹, X and n are as defined above and R² is selected from the groupconsisting of optionally substituted C₁-C₁₈ alkyl, optionallysubstituted C₂-C₁₈ alkenyl, optionally substituted aryl, optionallysubstituted heterocyclyl, optionally substituted aralkyl, optionallysubstituted alkaryl. Particularly preferred Z groups include, but arenot limited to, —CH₂(C₆H₅), C₁-C₂₀ alkyl,

where e is 2 to 4, and —SR³, where R³ is selected from C₁ to C₂₀ alkyl.

Preferred optional substituents for R² and Z groups include epoxy,hydroxy, alkoxy, acyl, acyloxy, carboxy (and salts), sulfonic acid (andsalts), alkoxy- or aryloxy-carbonyl, isocyanato, cyano, silyl, halo, anddialkylamino.

In selecting both R¹ and Z groups for RAFT agents of formula (4), thoseagents resulting from any combination of particularly preferred R¹ and Zgroups are also particularly preferred. Where the hydrophilic group is—N⁺R′R″R″′ there will be an associated counter anion.

Other suitable RAFT agents include those of formula (4) in which R¹ isan organic group optionally substituted with one or more hydrophobicgroups. In this case, Z is preferably an organic group optionallysubstituted with one or more hydrophilic groups.

As used herein, the terms “aryl” and “heteroaryl” refer to anysubstituent which includes or consists of one or more aromatic orheteroaromatic ring respectively, and which is attached via a ring atom.The rings may be mono or polycyclic ring systems, although mono orbicyclic 5 or 6 membered rings are preferred. Examples of suitable ringsinclude but are not limited to benzene, biphenyl, terphenyl,quaterphenyl, naphthalene, tetrahydronaphthalene, 1-benzylnaphthalene,anthracene, dihydroanthracene, benzanthracene, dibenzanthracene,phenanthracene, perylene, pyridine, 4-phenylpyridine, 3-phenylpyridine,thiophene, benzothiophene, naphthothiophene, thianthrene, furan,benzofuran, pyrene, isobenzofuran, chromene, xanthene, phenoxathiin,pyrrole, imidazole, pyrazole, pyrazine, pyrimidine, pyridazine, indole,indolizine, isoindole, purine, quinoline, isoquinoline, phthalazine,quinoxaline, quinazoline, pteridine, carbazole, carboline,phenanthridine, acridine, phenanthroline, phenazine, isothiazole,isooxazole, phenoxazine and the like, each of which may be optionallysubstituted

In this specification “optionally substituted” means that a group may ormay not be further substituted with one or more groups selected from,but not limited to, alkyl, alkenyl, alkynyl, aryl, halo, haloalkyl,haloalkenyl, haloalkynyl, haloaryl, hydroxy, alkoxy, alkenyloxy,aryloxy, benzyloxy, haloalkoxy, haloalkenyloxy, acetyleno, carboximidyl,haloaryloxy, isocyano, cyano, formyl, carboxyl, nitro, nitroalkyl,nitroalkenyl, nitroalkynyl, nitroaryl, alkylamino, dialkylamino,alkenylamino, alkynylamino, arylamino, diarylamino, benzylamino, imino,alkylimine, alkenylimine, alkynylimino, arylimino, benzylimino,dibenzylamino, acyl, alkenylacyl, alkynylacyl, arylacyl, acylamino,diacylamino, acyloxy, alkyl sulphonyloxy, arylsulphenyloxy,heterocyclyl, heterocycloxy, heterocyclamino, haloheterocyclyl, alkylsulphonyl, aryl sulphonyl, alkyl solphinyl, arylsulphinyl, carboalkoxy,alkylthio, benzylthio, acylthio, sulphonamido, sulfanyl, sulfo andphosphorus-containing groups, alkoxysilyl, silyl, alkylsilyl,alkylalkoxysilyl, phenoxysilyl, alkylphenoxysilyl, alkoxyphenoxysilyl,arylphenoxysilyl, allophanyl, guanidino, hydantoyl, ureido, andureylene.

Unless stated otherwise, the terms “halogen” and “halo” used hereinrefer to I, Br, Cl and F.

In this specification the term “alkyl”, used either alone or in compoundwords such as “alkenyloxyalkyl”, “alkylthio”, “alkylamino” and“dialkylamino” denotes straight chain, branched or cyclic alkyl,preferably C₁₋₂₀ alkyl or cycloalkyl. Examples of straight chain andbranched alkyl include methyl, ethyl, propyl, isopropyl, butyl,isobutyl, sec-butyl, tert-butyl, amyl, isoamyl, sec-amyl,1,2-dimethylpropyl, 1,1-dimethyl-propyl, hexyl, 4-methylpentyl,1-methylpentyl, 2-methylpentyl, 3-methylpentyl, 1,1-dimethylbutyl,2,2-dimethylbutyl, 3,3-dimethylbutyl, 1,2-dimethylbutyl,1,3-dimethylbutyl, 1,2,2,-trimethylpropyl, 1,1,2-trimethylpropyl,heptyl, 5-methoxyhexyl, 1-methylhexyl, 2,2-dimethylpentyl,3,3-dimethylpentyl, 4,4-dimethylpentyl, 1,2-dimethylpentyl,1,3-dimethylpentyl, 1,4-dimethyl-pentyl, 1,2,3,-trimethylbutyl,1,1,2-trimethylbutyl, 1,1,3-trimethylbutyl, octyl, 6-methylheptyl,1-methylheptyl, 1,1,3,3-tetramethylbutyl, nonyl, 1-, 2-, 3-, 4-, 5-, 6-or 7-methyl-octyl, 1-, 2-, 3-, 4- or 5-ethylheptyl, 1-, 2- or3-propylhexyl, decyl, 1-, 2-, 3-, 4-, 5-, 6-, 7- and 8-methylnonyl, 1-,2-, 3-, 4-, 5- or 6-ethyloctyl, 1-, 2-,3- or 4-propylheptyl, undecyl,1-, 2-, 3-, 4-, 5-, 6-, 7-, 8- or 9-methyldecyl, 1-, 2-, 3-, 4-, 5-, 6-or 7-ethylnonyl, 1-, 2-, 3-, 4- or 5-propyloctyl, 1-, 2- or3-butylheptyl, 1-pentylhexyl, dodecyl, 1-, 2-, 3-, 4-, 5-, 6-, 7-, 8-,9- or 10-methylundecyl, 1-, 2-, 3-, 4-, 5-, 6-, 7- or 8-ethyldecyl, 1-,2-, 3-, 4-, 5- or 6-propylnonyl, 1-, 2-, 3- or 4-butyloctyl,1-2-pentylheptyl and the like. Examples of cyclic alkyl include mono- orpolycyclic alkyl groups such as cyclopropyl, cyclobutyl, cyclopentyl,cyclohexyl, cycloheptyl, cyclooctyl, cyclononyl, cyclodecyl and thelike.

As used herein, the term “salt” denotes a species in ionised form, andincludes both acid addition and base addition salts. In the context ofthe present invention, suitable salts are those that do not interferewith the RAFT chemistry.

As used herein, the term “counter anion” denotes a species capable ofproviding a negative charge to balance the charge of the correspondingcation. Examples of counter anions include, Cl⁻, I⁻, Br⁻, F⁻, NO₃ ⁻, CN⁻and PO₃ ⁻.

As used herein, the term “alkoxy” denotes straight chain or branchedalkoxy, preferably C₁₋₂₀ alkoxy. Examples of alkoxy include methoxy,ethoxy, n-propoxy, isopropoxy and the different butoxy isomers.

As used herein, the term “alkenyl” denotes groups formed from straightchain, branched or cyclic alkenes including ethylenically mono-, di- orpoly-unsaturated alkyl or cycloalkyl groups as previously defined,preferably C₂₋₂₀ alkenyl. Examples of alkenyl include vinyl, allyl,1-methylvinyl, butenyl, iso-butenyl, 3-methyl-2-butenyl, 1-pentenyl,cyclopentenyl, 1-methyl-cyclopentenyl, 1-hexenyl, 3-hexenyl,cyclohexenyl, 1-heptenyl, 3-heptenyl, 1-octenyl, cyclooctenyl,1-nonenyl, 2-nonenyl, 3-nonenyl, 1-decenyl, 3-decenyl, 1,3-butadienyl,1-4,pentadienyl, 1,3-cyclopentadienyl, 1,3-hexadienyl, 1,4-hexadienyl,1,3-cyclohexadienyl, 1,4-cyclohexadienyl, 1,3-cycloheptadienyl,1,3,5-cycloheptatrienyl and 1,3,5,7-cyclooctatetraenyl.

As used herein, the term “alkynyl” denotes groups formed from straightchain, branched or cyclic alkyne including those structurally similar tothe alkyl and cycloalkyl groups as previously defined, preferably C₂₋₂₀alkynyl. Examples of alkynyl include ethynyl, 2-propynyl and 2- or3-butynyl.

As used herein, the term “acyl” either alone or in compound words suchas “acyloxy”, “acylthio”, “acylamino” or “diacylamino” denotescarbamoyl, aliphatic acyl group and acyl group containing an aromaticring, which is referred to as aromatic acyl or a heterocyclic ring whichis referred to as heterocyclic acyl, preferably C₁₋₂₀ acyl. Examples ofacyl include carbamoyl; straight chain or branched alkanoyl such asformyl, acetyl, propanoyl, butanoyl, 2-methylpropanoyl, pentanoyl,2,2-dimethylpropanoyl, hexanoyl, heptanoyl, octanoyl, nonanoyl,decanoyl, undecanoyl, dodecanoyl, tridecanoyl, tetradecanoyl,pentadecanoyl, hexadecanoyl, heptadecanoyl, octadecanoyl, nonadecanoyland icosanoyl; alkoxycarbonyl such as methoxycarbonyl, ethoxycarbonyl,t-butoxycarbonyl, t-pentyloxycarbonyl and heptyloxycarbonyl;cycloalkylcarbonyl such as cyclopropylcarbonyl, cyclobutylcarbonyl,cyclopentylcarbonyl and cyclohexylcarbonyl; alkylsulfonyl such as methylsulfonyl and ethyl sulfonyl; alkoxysulfonyl such as methoxysulfonyl andethoxysulfonyl; aroyl such as benzoyl, toluoyl and naphthoyl; aralkanoylsuch as phenylalkanoyl (e.g. phenylacetyl, phenylpropanoyl,phenylbutanoyl, phenylisobutylyl, phenylpentanoyl and phenylhexanoyl)and naphthylalkanoyl (e.g. naphthylacetyl, naphthylpropanoyl andnaphthylbutanoyl; aralkenoyl such as phenylalkenoyl (e.g.phenylpropenoyl, phenylbutenoyl, phenylmethacryloyl, phenylpentenoyl andphenylhexenoyl and naphthylalkenoyl (e.g. naphthylpropenoyl,naphthylbutenoyl and naphthylpentenoyl); aralkoxycarbonyl such asphenylalkoxycarbonyl (e.g. benzyloxycarbonyl); aryloxycarbonyl such asphenoxycarbonyl and napthyloxycarbonyl; aryloxyalkanoyl such asphenoxyacetyl and phenoxypropionyl; arylcarbamoyl such asphenylcarbamoyl; arylthiocarbamoyl such as phenylthiocarbamoyl;arylglyoxyloyl such as phenylglyoxyloyl and naphthylglyoxyloyl;arylsulfonyl such as phenylsulfonyl and napthylsulfonyl;heterocycliccarbonyl; heterocyclicalkanoyl such as thienylacetyl,thienylpropanoyl, thienylbutanoyl, thienylpentanoyl, thienylhexanoyl,thiazolylacetyl, thiadiazolylacetyl and tetrazolylacetyl;heterocyclicalkenoyl such as heterocyclicpropenoyl,heterocyclicbutenoyl, heterocyclicpentenoyl and heterocyclichexenoyl;and heterocyclicglyoxyloyl such as thiazolylglyoxyloyl andthienylglyoxyloyl.

As used herein, the terms “heterocyclic”, “heterocyclyl” and“heterocycl” used on their own or as part of a term such as“heterocyclicalkenoyl”, heterocycloxy” or “haloheterocyclyl” refer toaromatic, pseudo-aromatic and non-aromatic rings or ring systems whichcontain one or more heteroatoms selected from N, S, and O and which maybe optionally substituted. Preferably the rings or ring systems have 3to 20 carbon atoms. The rings or ring systems may be selected from thosedescribed above in relation to the definition of “heteroaryl”.

Most preferred RAFT agents include, but are not limited to, agentsrepresented by the following general formulas 5 to 13:

where R³, X and n are as previously defined.

Where a RAFT agent is to be used in accordance with the method of theinvention in an aqueous environment (e.g. in a continuous aqueousphase), it is preferable that it demonstrates hydrolytic stability.Trithiocarbonyl RAFT agents are particularly preferred for use in suchan environment.

The RAFT agents of formula (4) will have structural features that enablethem to physically associate with the particulate material. Where theRAFT agent is physically associated with the particulate material bybeing adsorbed onto its outermost surface, the required surface activityof the RAFT agent may be provided in a number of ways. For example, withreference to formula (4), the RAFT agent may derive its surface activitythrough one or more of the —Z group, —(X)_(n)— group, and the —R¹ group.The surface activity afforded by the Z, X_(n), and R¹ groups willtypically result from one or more of these groups themselves comprisinggroup(s), section(s), or region(s) having a combination of hydrophilicand hydrophobic properties.

Accordingly, in describing structural features of RAFT agents of formula(4) that provide for such surface activity, it can be useful todescribe, by way of example only, the distribution of hydrophilic andhydrophobic group(s), section(s) or region(s) throughout the structureof the RAFT agent. Those skilled in the art will appreciate that surfaceactivity of a compound may be derived from that compound having a welldefined section(s) or region(s) of hydrophilic and hydrophobiccharacter, or a less well defined section(s) or region(s) of hydrophilicand hydrophobic character. Structures of formula (4) having a welldefined section(s) or region(s) of hydrophobic and hydrophiliccharacter, for example as part of the —(X)_(n)— group, may beconveniently referred to as having a block copolymer structure, whereasthose having a less well defined section(s) or region(s) of hydrophobicand hydrophilic character may be conveniently referred to as havingalternating or random copolymer structures, or even a homopolymerstructure. Provided that the RAFT agent exhibits surface activity, thepresent invention is intended to embrace all such structures.

For example, if the —(X)_(n)— group were to provide the RAFT agent offormula (4) with its surface activity, the group may have a well definedblock copolymer structure such as AAAAAABBBBBB, an alternating copolymerstructure such as ABABABABABAB, a random block copolymer structure suchas AABABABBBAAB, or potentially even a homopolymer structure such asCCCCCCCCCCCC, where A represents a hydrophobic repeat unit, B representsa hydrophilic repeat unit, and C represents a repeat unit havingsufficient hydrophilic and hydrophobic properties to impart therequisite surface activity to the RAFT agent.

For convenience, those RAFT agents of formula (4) having surfaceactivity derived from a section(s) or region(s) of hydrophilic andhydrophobic character will hereinafter be referred to as amphipathicRAFT agents.

As used herein, the expression “amphipathic RAFT agent(s)” is intendedto denote a surface active RAFT agent that has a structure with bothhydrophilic and hydrophobic sections or regions. By the term “region(s)”or the expression “section(s) or region(s)” is meant that theamphipathic RAFT agent comprises as part of its molecular structure atleast two or three consecutive groups or repeat units having hydrophilicor hydrophobic properties. Generally, the sections or regions willcomprise at least two or three repeat units derived from hydrophilic orhydrophobic ethylenically unsaturated monomers.

As a surface active stabiliser, an amphipathic RAFT agent typicallycomprises both hydrophilic and hydrophobic sections or regions. One ofthese regions will generally have an affinity (i.e. attraction) towardthe particulate material and the other an affinity toward the continuousliquid phase. The region having an affinity toward the continuous liquidphase will generally comprise the stabilising moiety of the amphipathicRAFT agent. Depending on the nature of the particulate material (e.g.solid or liquid), the region having an affinity toward the particulatematerial may be adsorbed at the surface of the particulate material(e.g. solid) or be solvated by and penetrate into the particulatematerial (e.g. liquid). Where a region of the amphipathic RAFT agent issolvated by and penetrates into the particulate material, to ensure thatformation of polymer occurs at the surface of the particulate material,the reactive RAFT moiety (i.e. that which plays an active role in thepolymerisation reaction) should be associated with the region of theagent which has an affinity with the continuous liquid phase to therebylocate it outside of the particulate material.

Those skilled in the art will appreciate that such amphipathic charactermay be provided through different combinations of hydrophilic andhydrophobic regions. With reference to formula (4), an amphipathic RAFTagents preferably derive its amphipathic character from either:

-   -   1) a combination of a hydrophobic end and a hydrophilic end;        wherein the Z group provides hydrophobic properties to one end,        and R¹ and —(X)_(n)— provide hydrophilic properties to the other        end. In this case —(X)_(n)— may be derived from hydrophilic        monomer or be a tapered copolymer which gets progressively        hydrophilic towards R¹; or    -   2) a combination of a hydrophobic end and a hydrophilic end;        wherein the Z group provides hydrophilic properties to one end,        and R¹ and —(X)_(n)— provide hydrophobic properties to the other        end. In this case —(X)_(n)— may be derived from hydrophobic        monomer or may be a tapered copolymer which gets progressively        hydrophobic towards R¹; or    -   3) a combination of a hydrophobic end and a hydrophilic end;        wherein the Z group and —(X)_(n)— provide hydrophobic properties        to one end, and R¹ provides hydrophilic properties to the other        end; or    -   4) a combination of a hydrophobic end and a hydrophilic end;        wherein the Z group provides hydrophobic properties to one end,        —(X)_(n)— provides hydrophilic properties to the other end, and        R¹ is hydrophobic such that the net effect of —(X)_(n)— and R¹        is to provide hydrophilic character to that end; or    -   5) a combination of hydrophilic ends and a hydrophobic middle        section, wherein Z=—S—(X)_(n)—R¹, wherein each R¹ may be the        same or different and provides hydrophilic properties to each        end, and wherein —(X)_(n)— provides hydrophobic properties to        the middle section; or    -   6) a combination of hydrophobic and hydrophilic properties;        wherein the portion of the —(X)_(n)— group closest to R¹        provides the hydrophilic properties and the portion of the        —(X)_(n)— group closest to the thiocarbonylthio group provides        the hydrophobic properties. In this case, —(X)_(n)— of        formula (4) may be further represented as -(A)_(m)-(B)_(o)— to        provide a block copolymer that has the following general formula        (14):

-   -   -   where each A and B is independently a polymerised residue of            an ethylenically unsaturated monomer such that -(A)_(m)-            provides hydrophobic properties and —(B)_(o)— provides            hydrophilic properties, and m and o independently range from            1 to 99, preferably from 1 to 50, more preferably from 1 to            30, most preferably from 1 to 15, in each of the            aforementioned ranges m and o will generally be at least 2            or 3, and Z is as described above. Z may also be chosen such            that its polarity combines with that of -(A)_(m)- to enhance            the overall hydrophobic character to that end of the RAFT            agent. In addition to the hydrophilic character provided by            —(B)_(o)—, R¹ may also be hydrophilic and enhance the            overall hydrophilic character to that end of the RAFT agent,            or R¹ may be hydrophobic provided that the net effect of            —(B)_(o)— and R¹ results in an overall hydrophilic character            to that end of the RAFT agent; or

    -   7) a combination of hydrophobic and hydrophilic properties;        wherein, —(X)_(n)— of formula (4) may be further represented as        —(B)_(f)-[-(A)_(m)-(B)_(o)-]_(p)-(A)_(g)- to provide a copolymer        with small block regions that has the following general formula        (14a):

-   -   -   where each A and B is independently a polymerised residue of            an ethylenically unsaturated monomer such that A provides            hydrophobic properties and B provides hydrophilic            properties, f and g independently range from 0 to 10,            preferably from 0 to 5, m and o independently range from 1            to 10, preferably 1 to 5, each repeat unit p may be the same            or different, p ranges from 1 to 10, preferably 1 to 5, more            preferably 1 to 3, with the proviso that when p is 1 at            least one of f or g is at least 1, and Z and R¹ are as            defined above; the —(B)_(f)-[-(A)_(m)-(B)_(o)]_(p)-(A)_(g)-            group of RAFT agents of formula (14a) preferably provides            for a random block copolymer structure; or

    -   8) a combination of hydrophilic ends and a hydrophobic middle        section, wherein Z of general formula (14) is        —S-(A)_(m)-(B)_(o)—R¹, where -(A)_(m)- and —(B)_(o)- are as        defined above. Each R¹ may be the same or different and the        combination of —(B)_(o)—R¹ provides an overall hydrophilic        character to one end, and the combination of the other        —(B)_(o)—R¹ provides an overall hydrophilic character to the        other end. The hydrophobic portion of this type of amphipathic        RAFT agent is derived from -(A)_(m)-; or

    -   9) a variation on general formula (14a) wherein Z is        —S—(B)_(f)-[-(A)_(m)-(B)_(o)-]_(p)-(A)_(g)-R¹, where each A, B,        R¹, f, m, o and p may be the same or different and are as        defined in point (7) above.

Surface active character of the RAFT agent can also be provided throughstructures having less well defined block-like character. For example,the surface active character may be provided by a RAFT agent havingalternating hydrophilic and hydrophobic repeat units, or evenpotentially a repeat unit which has in its own right sufficienthydrophilic and hydrophobic properties to impart surface activeproperties to the RAFT agent. Accordingly, with reference to formula (4)the RAFT agents in accordance with the invention may also derive surfaceactive character from:

-   -   10) a combination of hydrophobic and hydrophilic properties;        wherein —(X)_(n)— may be further represented as -[-A-B—]_(q)— to        provide an alternating copolymer that has the following general        formula (14b):

-   -   -   where each A and B is independently a polymerised residue of            an ethylenically unsaturated hydrophobic and hydrophilic            monomer, respectively, and q is an integer ranging from 1 to            50, more preferably 2 to 25, most preferably from 2 to 10. Z            and R¹ are as defined above. The order of A and B may be            reversed such that —(X)_(n)— is —[—B-A-]_(q)-.

Those skilled in the art will appreciate that surface active charactermay be imparted to RAFT agents in other ways than the general examplesmentioned above in points 1) to 10). For example, the Z group in formula(14b) could be represented as —S-[-A-B—]_(q)—R¹.

The selection of a specific surface active RAFT agent for use inaccordance with the invention will to a large extent be dictated by thepolarity of both the continuous liquid phase and the particulatematerial. For example, the surface active character of a RAFT agent usedin association with a hydrophilic particulate material dispersed withina hydrophilic continuous liquid phase is likely to be different fromthat of a RAFT agent used in association with a hydrophobic particulatematerial dispersed within a hydrophilic continuous liquid phase.

Where the particulate material is a solid or semi-solid, the selectionof a specific surface active RAFT agent for use in accordance with theinvention might also be dictated by the combined factors of howefficiently the RAFT agent adsorbs at the surface of the particulatematerial and the amount of polymer that is to be formed at that surface.In particular, where a relatively thick layer of polymer is to be formedat the surface of a solid particulate material, the RAFT agent ispreferably selected such that the binding efficiency of the agent to theparticulate material enables the agent to move away from that surfacewith the polymer as it's layer thickness increases. If the bindingefficiency between the selected RAFT agent and the particulate materialwas sufficiently high to prevent such movement, the agent could beprogressively enveloped by the polymer as it is formed to therebyreduce, or possibly eliminate, the stabilising function of the agent.Maintaining stabilisation of the polymer/particle composite via the RAFTagent can be particularly important where a dispersion of polymer coatedparticles is being prepared.

It will be appreciated from the foregoing that a number of variablesneed to be considered when selecting an RAFT agent for use in accordancewith the invention. To further illustrate this point, a number ofdifferent approaches to performing the method are described in moredetail directly below. In describing the interaction between thecontinuous liquid phase and the dispersed particulate material, be itsolid, semi-solid, or liquid, it can also be convenient to refer to thepolarity or the hydrophilicity/hydrophobicity of such entities.

The method in accordance with the invention may be performed usinghydrophilic solid particulate material and a hydrophilic continuousliquid phase. In this case, a RAFT agent of formula (4) may be providedwith a hydrophobic region that is sufficiently large relative to thehydrophilic region to render the agent substantially insoluble in thehydrophilic continuous liquid phase. In order to perform the method, thehydrophilic particulate material can be dispersed in a mixture of thehydrophilic liquid and one or more solvents in which the amphipathicRAFT agent is soluble. The ratio of the hydrophilic liquid to the one ormore solvents is chosen such that the amphipathic RAFT agent is capableof being solvated in the mixture.

After the addition of the amphipathic RAFT agent to the mixture,additional hydrophilic liquid may then be added to cause the amphipathicRAFT agent to precipitate at the surface of the particulate material. Inparticular, by increasing the hydrophilic nature of the continuousliquid phase the solubility of the amphipathic RAFT agent decreases. Asa result of this decrease in solubility, the hydrophobic region of theagent precipitates at the surface of the particulate material and thehydrophilic region of the agent associates with the continuous liquidphase to stabilise the particulate material from coalescing. Uponforming a stabilised dispersion of the particulate material in thecontinuous liquid phase, monomer may be added and polymerised to formpolymer at the surface of the particulate material. The amphipathic RAFTagent may be selected such that its binding efficiency to the surface ofthe particulate material is relatively low to thereby enable the agentto move away from the surface of the particle with the polymer as it isformed.

A variation on the method described directly above might be where theamphipathic RAFT agent is substantially soluble in the hydrophiliccontinuous liquid phase, and where it comprises a non-ionisablehydrophilic region and a hydrophobic region that in itself comprises asmall proportion of polymerised hydrophilic ionisable monomer. In orderto perform the method, the amphipathic RAFT agent and the particulatematerial are introduced to the continuous liquid phase at a pH whichfacilitates the formation of an ionic charge at the surface of theparticulate material and an opposite ionic charge at the hydrophobicregion of the amphipathic RAFT agent. In this case, the small proportionof polymerised ionisable monomer in the hydrophobic region of theamphipathic RAFT agent can be sufficient to render the pH suitable todevelop such a charge at the surface of the particulate material and atthe hydrophobic region of the amphipathic RAFT agent.

Upon formation of the oppositely charged species, the amphipathic RAFTagent can adsorb at the surface of the particulate material such thatthe hydrophobic region thereof binds to the surface of the particulatematerial through an ionic mechanism, while the hydrophilic regionthereof associates with the continuous liquid phase to stabilise theparticulate material from coalescing. Depending upon the degree of ionicbonding that occurs between the amphipathic RAFT agent and theparticulate material, it may be in this case that the amphipathic RAFTagent will not be free to move away from the surface of the particulatematerial with the polymer as it is formed. Under these circumstances, itwill generally be preferred that the amount of polymer formed at thesurface of the particulate material does not envelope the amphipathicRAFT agent such that it can no longer function as a stabiliser.

Alternatively, to enable a thicker deposit of polymer at the surface ofthe particulate material the amphipathic character of the amphipathicRAFT agent may be suitably adjusted to reduce the ionic bindingefficiency, or a combination of two or more cooperative amphipathic RAFTagents may be used. An example of using two different amphipathic RAFTagents in such a cooperative manner is discussed directly below.

As a variation of the method, two different amphipathic RAFT agents maybe used in accordance with the method of the invention. In this case,both of the amphipathic RAFT agents may be soluble in the hydrophiliccontinuous liquid phase, with one of the agents comprising a hydrophobicregion and a non-ionisable hydrophilic region, and the other agentcomprising a hydrophobic region and a hydrophilic region which in itselfcomprises a proportion of polymerised hydrophilic ionisable monomer. Inorder to perform the method, the amphipathic RAFT agents may beintroduced to the hydrophilic liquid phase with the hydrophilicparticulate material at a pH that promotes ionic binding of thehydrophilic region of the second mentioned amphipathic RAFT agent to thesurface of the particulate material in a similar manner to thatdescribed above.

However, in this case the hydrophilic region of the second mentionedamphipathic RAFT agent adsorbs to the surface of the particulatematerial, and due to the hydrophilic nature of the continuous liquidphase the hydrophobic region of this amphipathic RAFT agent is believedto spread out over the particles surface to in effect render the surfaceof the particles with hydrophobic character. Stabilisation of theparticulate material in the continuous liquid phase can then be attainedas a result of the hydrophobic region of the first mentioned amphipathicRAFT agent adsorbing to the now hydrophobic surface of the particulatematerial and the non-ionisable hydrophilic region thereof associatingwith the hydrophilic continuous liquid phase.

Upon forming a stable dispersion of the particulate material in thecontinuous liquid phase, monomer may be introduced to form polymer atthe surface of the material. In this case, monomer may be polymerisedunder the control of both the amphipathic RAFT agents to form thepolymer. Where there is a relatively high bonding efficiency between theparticulate material and the second mentioned amphipathic RAFT agent,this agent may be enveloped by the polymer as it is formed. However, asthe first mentioned amphipathic RAFT agent is not adsorbed directly onthe surface of the particulate material, it will be generally more freeto move away from the surface of the particulate material with thepolymer as it is formed. By this arrangement, the non-ionisablehydrophilic region of the first mentioned amphipathic RAFT agent cancontinue to function as a stabiliser for the particulate material as athick layer of polymer is formed at the surface thereof.

If it is found that the dispersed encapsulated particles becomedestabilised as the thickness of the polymeric coating grows,stabilisation can often be maintained by incorporating an amount ofionisable monomer in the feed of hydrophobic monomer. Thus, although anoriginal moiety comprising a stabilising charge becomes buried in thecoating and rendered ineffective, the surface charge on the coatedparticles can be maintained by the later addition of ionisable monomermonomer. Preferably an amount of from 1% to 5% of the ionisable monomerin the hydrophobic monomer feed would be used for this purpose. Suitableionisable monomers would include but are not limited to acrylic acid,methacrylic acid and sodium styrene sulphonate.

By the term “ionisable”, used in connection with ethylenicallyunsaturated monomers or a group or region of a RAFT agent formed fromsuch monomers, is meant that the monomer, group or region has afunctional group which can be ionised to form a cationic or anionicgroup. Such functional groups will generally be capable of being ionisedunder acidic or basic conditions through loss or acceptance of a proton.Generally, the ionisable functional groups are acid groups or basicgroups. For example, a carboxylic acid functional group may form acarboxylate anion under basic conditions, and an amine functional groupmay form a quaternary ammonium cation under acidic conditions. Thefunctional groups may also be capable of being ionised through an ionexchange process.

By the term “non-ionisable”, used in connection with ethylenicallyunsaturated monomers or a group or region of a RAFT agent formed fromsuch monomers, is meant that the monomer, group or region does not haveionisable functional groups. In particular, such monomers, groups orregions do not have acid groups or basic groups which can loose oraccept a proton under acidic or basic conditions.

The method of the invention may also be used to form polymer at thesurface of hydrophobic solid particulate material dispersed in ahydrophilic continuous liquid phase. The RAFT agent in this case maycomprise a hydrophilic region and a hydrophobic region, with thehydrophobic region having a binding affinity toward the hydrophobicsurface of the particulate material and the hydrophilic regionassociating with the continuous liquid phase to stabilise theparticulate material from coalescing. Such an amphipathic RAFT agent maybe substantially soluble or insoluble in the continuous liquid phase,and the method may be performed in a similar manner to that outlinedabove.

The method of the invention may also be used to form polymer at thesurface of hydrophilic particulate material dispersed in a hydrophobiccontinuous liquid phase. The RAFT agent in this case may comprise ahydrophilic region and a hydrophobic region, with the hydrophilic regionhaving a binding affinity toward the surface of the particulate materialand the hydrophobic region associating with the continuous liquid phaseto stabilise the particulate material from coalescing. Upon forming astable dispersion of the particulate material in the continuous liquidphase monomer may be introduced to form the polymer at the surface ofthe particulate material.

In describing the interaction between a surface active RAFT agent andeach of the continuous liquid phase and the dispersed particulatematerial, it will be appreciated that as the structure of a RAFT agenttransitions from deriving its surface active properties from for examplea block copolymer structure through to a random or alternating copolymerstructure, or even a homopolymer structure, the role of theaforementioned more discrete hydrophilic and/or hydrophobic sections orregions of the agent become less well defined. For example, in a RAFTagent of formula (14b) the hydrophobic and hydrophilic moieties A and B,respectively, do not provide for discrete hydrophobic and hydrophilicregions, but nevertheless overall impart surface activity to the RAFTagent such that it can function as a stabiliser for the particulatematerial and gain control over polymerisation of the one or moreethylenically unsaturated monomers. In this case, the manner in whichsuch RAFT agents interact with each of the continuous liquid phase andthe particulate material to function as a stabiliser is not entirelyclear.

Where the method of the invention is performed using surface active RAFTagents having a less well defined block copolymer structure, the agentswill typically be selected such that the overall hydrophilicity (orhydrophobicty) of the RAFT agent is appropriate to the hydrophilicity(or hydrophobicty) of the surface of the particle to be coated. Forexample, a greater proportion of hydrophobic monomer might be used inthe preparation of a RAFT agent to be used in accordance with theinvention to form polymer at the surface of a hydrophobic particulatematerial than a hydrophilic particulate material.

In the general techniques outlined above for forming polymer at thesurface of solid particulate materials, where the continuous liquidphase consists essentially of the one or more ethylenically unsaturatedmonomers the polymerisation may take place as soon as the particulatematerial is dispersed throughout the monomer. It will be appreciatedthat the general principles expounded in such techniques may be employedwhen performing the invention using semisolid or liquid particulatematerials.

Depending upon the nature of the particulate material, the continuousliquid phase and the RAFT agent, it may be that prior to the formationof polymer at the surface of the particulate material, a surface activeRAFT agent, although acting as a stabiliser, may exhibit a degree oflability. By a surface active RAFT agent exhibiting a degree of“lability” is meant that the agent can exist in an equilibrium betweenbeing solvated in the continuous liquid phase and being associated atthe surface of the particulate material. For convenience, a RAFT agentthat is not associated with the particulate material will hereinafter bereferred to as “free” RAFT agent.

The presence of free RAFT agent in the continuous liquid phase canresult in the formation of micelles and facilitate the formation ofpolymer which is not at the surface of the particulate material (i.e.independent polymer particles). Accordingly, surface active RAFT agentsused in accordance with the invention are preferably selected toprevent, or at least minimise, independent polymer particle formation.It will be appreciated that provided a labile RAFT agent gains controlof polymerisation at the surface of the particulate material, thispolymerisation process itself will inevitably render the agentnon-labile.

It has been found that RAFT agents having a less well defined blockcharacter, such as those described in points 7) and 10) above, uponbecoming adsorbed onto the surface of the particulate material, are lessprone to desorption and forming micelles in the continuous liquid phase.In other words, surface active RAFT agents having a less well definedblock-like structure tend to be less labile than their “blocky”counterparts. The use of RAFT agents having a less well defined blockstructure has been found to be particularly useful in preparingdispersions of polymer encapsulated particulate materials with a highsolids content (i.e. greater than about 50 weight percent).

Where the method of the invention is performed using a continuous liquidphase which does not consist essentially of the one or moreethylenically unsaturated monomers that is to be polymerised to form thepolymer, it is preferred that the monomer is introduced to thecontinuous liquid phase after the particulate material and any surfaceactive RAFT agent interact so as to provide for a stable dispersion. Byadopting this approach, the likelihood of any surface active RAFT agentalso acting as a stabiliser for monomer droplets in the continuousliquid phase is reduced. It is also preferred that the monomer which isintroduced to the continuous liquid phase is done in a manner thatavoids the formation of monomer droplets. In other words, it ispreferred that the polymerisation is conducted under “starved feed”conditions. Such conditions also reduce the likelihood of stabilisedmonomer droplets being formed in the continuous liquid phase, which inturn also reduces the possibility of forming polymer that is independentof the particulate material.

Where it is desirable to minimise the possibility of forming polymerthat is independent of the particulate material, the polymerisation maybe conducted to a point where substantially all labile RAFT agentpresent has been rendered non-labile. At this point, the “lightly”polymer encapsulated particles may be separated from any independentpolymer particles that may have formed or any residual free RAFT agentby a separation method such as centrifugation. The “lightly” polymerencapsulated particles could then be redispersed in a continuous liquidphase with monomer and the polymerisation continued to form a thickerpolymer coating on the particulate material.

In accordance with the method of the invention, ethylenicallyunsaturated monomers are polymerised under the control of the RAFT agentto form polymer at the surface of the particulate material. Thepolymerisation will usually require initiation from a source of freeradicals. The source of initiating radicals can be provided by anysuitable method of generating free radicals, such as the thermallyinduced homolytic scission of suitable compound(s) (thermal initiatorssuch as peroxides, peroxyesters, or azo compounds), the spontaneousgeneration from monomers (e.g. styrene), redox initiating systems,photochemical initiating systems or high energy radiation such aselectron beam, X- or gamma-radiation. The initiating system is chosensuch that under the reaction conditions there is no substantial adverseinteraction of the initiator or the initiating radicals with theamphipathic RAFT agent.

Thermal initiators are chosen to have an appropriate half life at thetemperature of polymerisation. These initiators can include one or moreof the following compounds:

-   -   2,2′-azobis(isobutyronitrile), 2,2′-azobis(2-cyanobutane),        dimethyl 2,2′-azobis(isobutyrate), 4,4′-azobis(4-cyanovaleric        acid), 1,1′-azobis(cyclohexanecarbonitrile),        2-(t-butylazo)-2-cyanopropane,        2,2′-azobis{2-methyl-N-[1,1-bis(hydroxymethyl)-2-hydroxyethyl]propionamide},        2,2′-azobis[2-methyl-N-(2-hydroxyethyl)propionamide],        2,2′-azobis(N,N′-dimethyleneisobutyramidine) dihydrochloride,        2,2′-azobis(2-amidinopropane) dihydrochloride,        2,2′-azobis(N,N′-dimethyleneisobutyramidine),        2,2′-azobis{2-methyl-N-[1,1-bis(hydroxymethyl)-2-hydroxyethyl]propionamide},        2,2′-azobis{2-methyl-N-[1,1-bis(hydroxymethyl)-2-ethyl]propionamide},        2,2′-azobis[2-methyl-N-(2-hydroxyethyl)propionamide],        2,2′-azobis(isobutyramide) dihydrate,        2,2′-azobis(2,2,4-trimethylpentane),        2,2′-azobis(2-methylpropane), t-butyl peroxyacetate, t-butyl        peroxybenzoate, t-butyl peroxyneodecanoate, t-butylperoxy        isobutyrate, t-amyl peroxypivalate, t-butyl peroxypivalate,        diisopropyl peroxydicarbonate, dicyclohexyl peroxydicarbonate,        dicumyl peroxide, dibenzoyl peroxide, dilauroyl peroxide,        potassium peroxydisulfate, ammonium peroxydisulfate, di-t-butyl        hyponitrite, dicumyl hyponitrite. This list is not exhaustive.

Photochemical initiator systems are chosen to have the requisitesolubility in the reaction medium and have an appropriate quantum yieldfor radical production under the conditions of the polymerisation.Examples include benzoin derivatives, benzophenone, acyl phosphineoxides, and photo-redox systems.

Redox initiator systems are chosen to have the requisite solubility inthe reaction medium and have an appropriate rate of radical productionunder the conditions of the polymerisation; these initiating systems caninclude, but are not limited to, combinations of the following oxidantsand reductants:

-   -   oxidants: potassium peroxydisulfate, hydrogen peroxide, t-butyl        hydroperoxide. reductants: iron (II), titanium (III), potassium        thiosulfite, potassium bisulfite.

Other suitable initiating systems are described in recent texts. See,for example, Moad and Solomon “the Chemistry of Free RadicalPolymerisation”, Pergamon, London, 1995, pp 53-95.

Suitable initiators which have an appreciable solubility in ahydrophilic reaction medium such as water include, but are not limitedto, 4,4-azobis(cyanovaleric acid),2,2′-azobis{2-methyl-N-[1,1-bis(hydroxymethyl)-2-hydroxyethyl]propionamide},2,2′-azobis[2-methyl-N-(2-hydroxyethyl)propionamide],2,2′-azobis(N,N′-dimethyleneisobutyramidine),2,2′-azobis(N,N′-dimethyleneisobutyramidine) dihydrochloride,2,2′-azobis(2-amidinopropane) dihydrochloride,2,2′-azobis{2-methyl-N-[1,1-bis(hydroxymethyl)-2-ethyl]propionamide},2,2′-azobis[2-methyl-N-(2-hydroxyethyl)propionamide],2,2′-azobis(isobutyramide) dihydrate, and derivatives thereof.

Suitable initiators which have an appreciable solubility in ahydrophobic reaction medium may vary depending on the polarity of thereaction medium, but typically would include oil soluble initiators suchas azo compounds exemplified by the well known material2,2′-azobisisobutyronitrile. Other readily available initiators are acylperoxides such as acetyl and benzoyl peroxide as well as alkyl peroxidessuch as cumyl and t-butyl peroxides. Hydroperoxides such as t-butyl andcumyl hydroperoxides may also be used.

The continuous liquid phase in a given polymerization process may alsocontain other additives, for example additives to regulate pH.

In relation to the polymerisation process which occurs during the courseof the method of the invention, it is important that polymer is formedat the surface of the particulate material and that this polymerisationproceeds under the control of the RAFT agent. Without wishing to belimited by theory, it is believed that the polymerisation process thatoperates during the method begins through the formation of a propagatingmonomer radical which diffuses through the continuous liquid phase andpositions itself at the surface of the particulate material. As the RAFTagents are also positioned at the surface of the particulate materialthey can readily gain control over the polymerisation such thatpolymerisation of the monomers proceed under a RAFT mediated freeradical process. To facilitate this process, it is preferred that thenumber of RAFT species present at the surface of the particulatematerial is greater than the sum of initiating radicals that reach thatsurface throughout the course of the polymerisation reaction. Ingeneral, the total number of initiating radicals that position themselfat the surface of the particulate material should be less than the totalnumber of RAFT agents present in the continuous liquid phase.Preferably, the total number of initiating radicals is less than 50percent, more preferably less than 20 percent, of the total number ofRAFT agents present in the continuous liquid phase.

In connection with facilitating the polymerisation of monomers under thecontrol of the RAFT agents to form polymer at the surface of theparticulate material, it is preferred that at any given point during thepolymerisation process the amount of free RAFT agent present in thecontinuous liquid phase is relatively low compared with that which isadsorbed on the surface of the dispersed particulate material.Preferably, there is less than 50 wt %, more preferably less than 20 wt%, most preferably less than 10 wt % of “free” RAFT agent present in thecontinuous liquid phase at any point in time during the polymerisationprocess.

It is preferable that polymerisation of the monomers is maintained underthe control of the RAFT agent throughout the entire polymerisation.However, provided that polymer at the surface of the particulatematerial is at least in part formed under the control of a RAFT agent,monomer may also be polymerised by other free radical pathways. Havingsaid this, it will be appreciated that as the amount of monomerpolymerised under the control of the RAFT agent decreases, thepropensity for irregular growth and the formation of polymer in onereaction site only increases. The amount of monomer that may bepolymerised by other free radical pathways in a given reaction sequencewill to a large extent depend upon the intended application for thepolymer encapsulated particulate material.

Evidence as to whether a polymerisation reaction in accordance with themethod of the invention has proceeded, at least in part, under thecontrol of a RAFT agent may be obtained by a simple visual assessment(for example by Transmission Electron Microscopy) of the polymer coatingof the polymer encapsulated particulate material. Significant loss of“RAFT control” will be characterised by an irregular non-uniform polymercoating, whereas polymerisation under the control of the RAFT agentprovides a regular uniform polymer coating.

Evidence of “RAFT control” may also be readily obtained by sampling thepolymer/particulate material composite during the polymerisationreaction and analysing the resulting polymer by a suitable techniquesuch as Gel Permeation Chromatography (GPC). Ideally, where “RAFTcontrol” has been established, the polymer will have a lowerpolydispersity compared with a polymer prepared by a convention freeradical mediated pathway. The other feature of “RAFT control” shown byGPC data is that molecular weight of the polymer should grow linearlywith conversion. This is believed to be an important feature inperforming the method of the invention. The polymer formed in accordancewith the invention will generally show a linear growth of molecularweight with conversion even though the polydispersity of the polymer maybroaden during the course of the polymerisation process.

The composition and architecture of the polymer formed at the surface ofthe particulate material may be tailored through the selection andcontrolled addition of monomer. A wide range of ethylenicallyunsaturated monomers may be used in accordance with the method. Suitablemonomers are those which can be polymerised by a free radical process.The monomers should also be capable of being polymerised with othermonomers. The factors which determine copolymerisability of variousmonomers are well documented in the art. For example, see: Greenlee, R.Z., in Polymer Handbook 3r^(d) Edition (Brandup, J., and Immergut. E. H.Eds) Wiley: New York, 1989 p 11/53. Such monomers include those with thegeneral formula (15):

-   -   where U and W are independently selected from the group        consisting of —CO₂H, —CO₂R², —COR², —CSR², —CSOR², —COSR²,        —CONH₂, —CONHR², —CONR² ₂, hydrogen, halogen and optionally        substituted C₁-C₄ alkyl wherein the substituents are        independently selected from the group consisting of hydroxy,        —CO₂H, —CO₂R¹, —COR², —CSR², —CSOR², —COSR², —CN, —CONH₂,        —CONHR², —CONR² ₂, —OR², —SR², —O₂CR², —SCOR², and —OCSR²; and    -   V is selected from the group consisting of hydrogen, R², —CO₂H,        —CO₂R², —COR², —CSR², —CSOR², —COSR², —CONH₂, —CONHR², —CONR² ₂,        —OR², —SR², —O₂CR², —SCOR², and —OCSR²;    -   where R² is selected from the group consisting of optionally        substituted C₁-C₁₈ alkyl, optionally substituted C₂-C₁₈ alkenyl,        optionally substituted aryl, optionally substituted heteroaryl,        optionally substituted carbocyclyl, optionally substituted        heterocyclyl, optionally substituted aralkyl, optionally        substituted heteroarylalkyl, optionally substituted alkaryl,        optionally substituted alkylheteroaryl and polymer chains        wherein the substituents are independently selected from the        group consisting of alkyleneoxidyl (epoxy), hydroxy, alkoxy,        acyl, acyloxy, formyl, alkylcarbonyl, carboxy, sulfonic acid,        alkoxy- or aryloxy-carbonyl, isocyanato, cyano, silyl, halo,        amino, including salts and derivatives thereof. Preferred        polymer chains include, but are not limited to, polyalkylene        oxide, polyarylene ether and polyalkylene ether.

Examples of monomers include, but are not limited to, maleic anhydride,N-alkylmaleimide, N-arylmaleimide, dialkyl fumarate andcyclopolymerisable monomers, acrylate and methacrylate esters, acrylicand methacrylic acid, styrene, acrylamide, methacrylamide, andmethacrylonitrile, mixtures of these monomers, and mixtures of thesemonomers with other monomers. As one skilled in the art would recognise,the choice of comonomers is determined by their steric and electronicproperties. The factors which determine copolymerisability of variousmonomers are well documented in the art. For example, see: Greenlee, RZ. in Polymer Handbook 3r^(d) Edition (Brandup, J., and Immergut, E. HEds.) Wiley: New York. 1989 pII/53.

Specific examples of useful ethylenically unsaturated monomers includethe following: methyl methacrylate, ethyl methacrylate, propylmethacrylate (all isomers), butyl methacrylate (all isomers),2-ethylhexyl methacrylate, isobornyl methacrylate, methacrylic acid,benzyl methacrylate, phenyl methacrylate, methacrylonitrile,alpha-methylstyrene, methyl acrylate, ethyl acrylate, propyl acrylate(all isomers), butyl acrylate (all isomers), 2-ethylhexyl acrylate,isobornyl acrylate, acrylic acid, benzyl acrylate, phenyl acrylate,acrylonitrile, styrene, functional methacrylates, acrylates and styrenesselected from glycidyl methacrylate, 2-hydroxyethyl methacrylate,hydroxypropyl methacrylate (all isomers), hydroxybutyl methacrylate (allisomers), N,N-dimethylaminoethyl methacrylate, N,N-diethylaminoethylmethacrylate, triethyleneglycol methacrylate, itaconic anhydride,itaconic acid, glycidyl acrylate, 2-hydroxyethyl acrylate, hydroxypropylacrylate (all isomers), hydroxybutyl acrylate (all isomers),N,N-dimethylaminoethyl acrylate, N,N-diethylaminoethyl acrylate,triethyleneglycol acrylate, methacrylamide, N-methylacrylamide,N,N-dimethylacrylamide, N-tert-butylmethacrylamide,N-n-butylmethacrylamide, N-methylolmethacrylamide,N-ethylolmethacrylamide, N-tert-butylacrylamide, N-n-butylacrylamide,N-m ethylolacrylamide, N-ethylolacrylamide, vinyl benzoic acid (allisomers), diethylamino styrene (all isomers), alpha-methylvinyl benzoicacid (all isomers), diethylamino alpha-methyl styrene (all isomers),p-vinylbenzene sulfonic acid, p-vinylbenzene sulfonic sodium salt,trimethoxysilylpropyl methacrylate, triethoxysilylpropyl methacrylate,tributoxysilylpropyl methacrylate, dimethoxymethyl silylpropylmethacrylate, diethoxymethyl silylpropyl methacrylate,dibutoxymethylsilylpropyl methacrylate, diisopropoxymethylsilylpropylmethacrylate, dimethoxysilylpropyl methacrylate, diethoxysilylpropylmethacrylate, dibutoxysilylpropyl methacrylate, diisopropoxysilylpropylmethacrylate, trimethoxysilylpropyl acrylate, triethoxysilylpropylacrylate, tributoxysilylpropylacrylate, dimethoxymethylsilylpropylacrylate, diethoxymethylsilylpropyl acrylate, dibutoxymethylsilylpropylacrylate, diisopropoxymethylsilylpropyl acrylate, dimethoxysilylpropylacrylate, diethoxysilylpropyl acrylate, dibutoxysilylpropyl acrylate,diisopropoxysilylpropyl acrylate, vinyl acetate, vinyl butyrate, vinylbenzoate, vinyl chloride, vinyl fluoride, vinyl bromide, maleicanhydride, N-phenylmaleimide, N-butylmaleimide, N-vinylpyrrolidone,N-vinylcarbazole, butadiene, ethylene and chloroprene. This list is notexhaustive.

To facilitate the formation of polymer at the surface of the solidparticulate material, the one or more ethylenically unsaturated monomersare preferably selected such that when they polymerise they form polymerthat is substantially insoluble in the continuous liquid phase.

Those skilled in the art will appreciate that monomers that are selectedto form the encapsulating polymer will strongly influence its glasstransition temperature (Tg). The “Tg” is a narrow range of temperatureover which an amorphous polymer (or the amorphous regions in a partiallycrystalline polymer) changes from a relatively hard and brittle state toa relatively viscous or rubbery state. The Tg of the encapsulatingpolymer can conveniently be tailored to suit the intended applicationfor the polymer encapsulated particulate material. For example, monomersthat are polymerised to form the encapsulating polymer may be selectedto provide a Tg that enables an aqueous dispersion of the polymerencapsulated particulate material (as in a paint formulation) tocoalesce and form a film.

Tg values referred to herein are calculated, and those relating to acopolymer are calculated in accordance with the Fox equation(1/Tg=W_(n)/Tg_((n))). Unless otherwise stated, where an encapsulatingpolymer comprises a mixture of polymers or copolymers having differentTg's, the Tg of the overall polymer composition is calculated as aweighted average value.

For example, a polymer mixture comprising a copolymer (50 wt. %) with acalculated Fox Tg of −10° C. and a copolymer (50 wt. %) with acalculated Fox Tg of 50° C., will provide an overall Tg of 20° C.

Those skilled in the art will be capable of selecting monomers to affordan encapsulating polymer with the appropriate Tg for the intendedapplication of the polymer encapsulated particulate material.

Where the polymer/particulate material composites that may be preparedin accordance with the invention are to be used in contact with solventsin which the encapsulating polymer may be soluble, or for othercommercially relevant reasons, it may be desirable to introduce a degreeof crosslinking into the polymer. The crosslinked polymer structure maybe derived by any known means, but it is preferable that it is derivedthrough the use of polymerised ethylenically unsaturated monomers. Thoseskilled in the art will appreciate that crosslinked polymer structuresmay be derived in a number of ways through the use of polymerisedethylenically unsaturated monomers. For example, multi-ethylenicallyunsaturated monomers can afford a crosslinked polymer structure throughpolymerisation of at least two unsaturated groups to provide acrosslink. In this case, the crosslinked structure is typically derivedduring polymerisation and provided through a free radical reactionmechanism.

Alternatively, the crosslinked polymer structure may be derived fromethylenically unsaturated monomers which also contain a reactivefunctional group that is not susceptible to taking part in free radicalreactions (i.e. “functionalised” unsaturated monomers). In this case,the monomers are incorporated into the polymer backbone throughpolymerisation of the unsaturated group, and the resulting pendantfunctional group provides means through which crosslinking may occur. Byutilising monomers that provide complementary pairs of reactivefunctional groups (i.e. groups that will react with each other), thepairs of reactive functional groups can react through non radicalreaction mechanisms to provide crosslinks. Formation of such crosslinkswill generally occur during polymerisation of the monomers.

A variation on using complementary pairs of reactive functional groupsis where the monomers are provided with non-complementary reactivefunctional groups. In this case, the functional groups will not reactwith each other but instead provide sites which can subsequently bereacted with a crosslinking agent to form the crosslinks. It will beappreciated that such crosslinking agents will be used in an amount toreact with substantially all of the non-complementary reactivefunctional groups. Formation of the crosslinks under these circumstanceswill generally be induced after polymerisation of the monomers.

A combination of these methods of forming a crosslinked polymerstructure may be used.

The terms “multi-ethylenically unsaturated monomers” and “functionalisedunsaturated monomers” mentioned above can conveniently and collectivelyalso be referred to herein as “crosslinking ethylenically unsaturatedmonomers” or “crosslinking monomers”. By the general expression“crosslinking ethylenically unsaturated monomers” or “crosslinkingmonomers” is meant an ethylenically unsaturated monomer through which acrosslink is or will be derived. Accordingly, a multi-ethylenicallyunsaturated monomer will typically afford a crosslink duringpolymerisation, whereas a functionalised unsaturated monomer can providemeans through which a crosslink can be derived either during or afterpolymerisation. It will be appreciated that not all unsaturated monomersthat contain a functional group will be used in accordance with theinvention for the purpose of functioning as a crosslinking monomer. Forexample, acrylic acid should not be considered as a crosslinking monomerunless it is used to provide a site through which a crosslink is to bederived.

Examples of suitable multi-ethylenically unsaturated monomers that maybe selected to provide the crosslinked polymer structure include, butare not limited to, ethylene glycol di(meth)acrylate, triethylene glycoldi(meth)acrylate, tetraethylene glycol di(meth)acrylate, 1,3-butyleneglycol di(meth)acrylate, trimethylolpropane tri(meth)acrylate,1,4-butanediol di(meth)acrylate, neopentyl glycol di(meth)acrylate,1,6-hexanediol di(meth)acrylate, pentaerythritol di(meth)acrylate,pentaerythritol tri(meth)acrylate, pentaerythritol tetra(meth)acrylate,glycerol di(meth)acrylate, glycerol allyloxy di(meth)acrylate,1,1,1-tris(hydroxymethyl)ethane di(meth)acrylate,1,1,1-tris(hydroxymethyl)ethane tri(meth)acrylate,1,1,1-tris(hydroxymethyl)propane di(meth)acrylate,1,1,1-tris(hydroxymethyl)propane tri(meth)acrylate, triallyl cyanurate,triallyl isocyanurate, triallyl trimellitate, diallyl phthalate, diallylterephthalte, divinyl benzene, methylol (meth)acrylamide, triallylamine,oleyl maleate, glyceryl propoxy triacrylate, allyl methacrylate,methacrylic anhydride and methylenebis (meth) acrylamide.

Examples of suitable ethylenically unsaturated monomers which contain areactive functional group that is not susceptible to taking part in freeradical reactions include, but are not limited to, acetoacetoxyethylmethacrylate, glycidyl methacrylate, N-methylolacrylamide,(isobutoxymethyl)acrylamide, hydroxyethyl acrylate,t-butyl-carbodiimidoethyl methacrylate, acrylic acid,γ-methacryloxypropyltriisopropoxysilane, 2-isocyanoethyl methacrylateand diacetone acrylamide.

Examples of suitable pairs of monomers mentioned directly above thatprovide complementary reactive functional groups includeN-methylolacrylamide and itself, (i sobutoxymethyl)acrylamide anditself, γ-methacryloxypropyltriisopropoxysilane and itself,2-isocyanoethyl methacrylate and hydroxyethyl acrylate, andt-butyl-carbodiimidoethyl methacrylate and acrylic acid.

Examples of suitable crosslinking agents that can react with thereactive functional groups of one or more of the functionalisedunsaturated monomers mentioned above include, but are not limited to,amines such as hexamethylene diamine, ammonia, methyl amine, ethylamine, Jeffamines™ and diethylene triamine, melamine, trimethylolpropanetris(2-methyl-1-aziridine propionate) and adipic bishydrazide. Examplesof pairs of crosslinking agents and functionalised unsaturated monomersthat provide complementary reactive groups include hexamethylene diamineand acetoacetoxyethyl methacrylate, amines such as hexamethylenediamine, ammonia, methyl amine, ethyl amine, Jeffamines™ and diethylenetriamine and glycidyl methacrylate, melamine and hydroxyethyl acrylate,trimethylolpropane tris(2-methyl -1-aziridine propionate) and acrylicacid, adipic bishydrazide and diacetone acrylamide.

General techniques used in performing conventional emulsion,mini-emulsion and suspension polymerisations can advantageously beemployed in performing the method of the invention. However, whenselecting suitable reagents for employing such techniques it should beappreciated that the method of the invention is in effect an interfacialpolymerisation process in which polymer is formed at the surface ofparticulate material that is dispersed throughout a continuous liquidphase.

The method of the invention may be operated in batch, semi-continuous orcontinuous modes. Where the continuous liquid phase consists essentiallyof the one or more ethylenically unsaturated monomers that arepolymerised to form the polymer, the method is preferably operated inbatch mode, and where the continuous liquid phase does not consistessentially of the one or more ethylenically unsaturated monomers thatare polymerised to form the polymer, the method is preferably operatedin semi-continuous or continuous modes.

Semi-continuous and continuous modes of operation offer superior controlof polymer architecture together with control over the polymerpolydispersity. According to these modes of operation, monomer may beadded gradually or in stages thereby enabling different monomers andother additives to be introduced during the course of the polymerisationreaction. As the solid content of the dispersion increases, theresulting polymer/particulate material composite may not be adequatelystabilised. In this case, further RAFT agent may be also added to thereaction with the monomer in order to replenish the surface of theparticle with stabilising moieties.

By “semi-continuous” is meant that the method is conducted batch wiseand monomer is added gradually or in stages throughout thepolymerisation. By “continuous” is meant that the method is performed ina loop type reactor whereby all reagents are continuously addedgradually or in stages throughout the polymerisation and product iscontinuously removed from the reaction system. Preferably, the method isperformed in a semi-continuous mode.

A preferred method of carrying out a semi-continuous mode ofpolymerisation comprises adding a selected particulate material and RAFTagent to a suitable continuous liquid phase in a reaction vessel toprovide for a stable dispersion of the particulate material throughoutthe continuous liquid phase. A thermal initiator may also be added,along with any other reagents if required, for example buffers toregulate pH. Typically, all reagents used are essentially free fromdissolved oxygen and the reaction solution is purged with an inert gas,such as nitrogen, prior to initiating the polymerisation. The dispersiontemperature is then increased so that the initiator undergoes thermallyinduced homolytic scission. Monomer may then be added and polymerisationcan proceed under the control of the RAFT agent. The addition of monomerat this stage may be maintained at a rate to avoid reservoir monomerdroplets from forming, and can be continued at such a rate untilsufficient monomer has been polymerised under the control of the RAFTagent to render it, if it was not already, essentially non-labile fromthe surface of the particulate material. Further monomer, which may bethe same or different, can then be added at a greater rate eithercontinually or in stages until the desired degree of polymerisation hasoccurred. For example, the polymerisation may be continued to providefor a dispersion of polymer/particulate material composite particleshaving a desired solids content.

A specific example of employing the method of the invention in thismanner might be in the coating of titanium dioxide particles withpolymer. In this case, the hydrophilic titanium dioxide particulatematerial could be dispersed in a hydrophilic continuous liquid phasesuch as water using an appropriate RAFT agent. Upon forming a stabledispersion, hydrophobic monomers such as butyl acrylate and methylmethacrylate may be introduced to the dispersion to form polymer at thesurface of the titanium dioxide particles. The polymer may be formed tocoat and encapsulate the titanium dioxide particles and furthercontinued to afford a latex having a desired solids content. Theresulting latex would therefore comprise an aqueous dispersion ofpolymer encapsulated titanium dioxide particles which couldadvantageously be used directly in paint formulations as an opacifiedbinder.

Where the continuous liquid phase used in accordance with the method ofthe invention consists essentially of the one or more ethylenicallyunsaturated monomers that are polymerised to form the polymer, themethod will typically be performed as a batch process and in effect maybe considered as a bulk polymerisation process. Where such a continuousliquid phase is dispersed in a further continuous liquid phase ashereinbefore described, the method may in effect be seen as aminiemulsion or suspension polymerisation process. In these cases, RAFTagent will generally not be introduced to the continuous liquid phaseduring the course of the polymerisation, and it is therefore preferablethat sufficient RAFT agent is used to stabilise the particulate materialin the continuous liquid phase prior to initiation of the polymerisationreaction.

One approach to performing the method of the invention in bulk mode willtypically involve adding the particulate material, the RAFT agent and athermal initiator to one or more ethylenically unsaturated monomers in areaction vessel. Other reagents may also be added if required.Typically, all reagents used are essentially free from dissolved oxygenand the reaction solution is purged with an inert gas, such as nitrogen,prior to initiating polymerisation. Having adequately dispersed theparticulate material throughout the one or more ethylenicallyunsaturated monomers using means well known to those skilled in the art,the dispersion temperature may then be increased so that the initiatorundergoes thermally induced homolytic scission. Given that thecontinuous liquid phase in this case consists essentially of monomer, apropagating monomer radical is immediately formed. The propagatingmonomer radical can then diffuse to the surface of the particulatematerial and enable the RAFT agent stabilising the particles to gaincontrol over the polymerisation. The polymerisation continues untilsubstantially all of the monomer has been consumed to thereby provide apolymer matrix having the solid particulate material substantiallyuniformly dispersed therethrough.

The approach outlined directly above has particular advantages when itis desired to encapsulate high concentrations of nanoparticles within apolymer matrix. Using conventional techniques, the amount of dispersantrequired to stabilise the nanoparticles in the monomer phase would beexpected to radically alter the properties of the matrix polymer even ifthe dispersant did maintain a stable dispersion during polymerisation ofthe monomer. Given that the RAFT agent used in accordance with theinvention can act as a stabiliser for the particulate material and alsotake part in the polymerisation process to ultimately form part of theencapsulating polymer, problems associated with the presence of a“foreign” dispersant in the polymer matrix can advantageously beavoided.

Performing the method in the aforementioned bulk mode could be readilyadapted by one skilled in the art such that the continuous liquid phaseis dispersed in a further continuous liquid phase to prepare polymerparticles having the particulate material substantially uniformlydispersed therethrough.

Those skilled in the art will appreciate that numerous parameters may bevaried when performing the method of the invention in either continuous,semi-continuous or bulk modes.

There is no particular limitation as to the nature of the continuousliquid phase that may be used in accordance with the method providedthat the particulate material may be dispersed in it and that it doesnot adversely affect the formation of polymer at the surface of theparticulate material. For convenience, a continuous liquid phase thatconsists essentially of the one or more ethylenically unsaturatedmonomers that is polymerised to form the polymer will hereinafter bereferred to as a “reactive” continuous liquid phase. Conversely, acontinuous liquid phase which does not consist essentially of the one ormore ethylenically unsaturated monomers that are polymerised to form thepolymer will hereinafter be referred to as a “non-reactive” continuousliquid phase. The continuous liquid phase may have hydrophilic orhydrophobic character.

Suitable non-reactive continuous liquid phases include, but are notlimited to, water, toluene, white spirit and other well known optionallysubstituted aromatic or optionally substituted aliphatic organicliquids.

Suitable monomers that may be used in providing a reactive continuousliquid phase include, but are not limited to, the foregoing list ofethylenically unsaturated monomers. Examples of ethylenicallyunsaturated monomers that might be considered by a person skilled in theart to be hydrophilic include, but are not limited to, acrylic acid,methacrylic acid, hydroxyethyl methacrylate, hydroxypropyl methacrylate,acrylamide and methacrylamide, hydroxyethyl acrylate, N-methylacrylamideor dimethylaminoethyl methacrylate. Examples of ethylenicallyunsaturated monomers that might be considered by a person skilled in theart to be hydrophobic include, but are not limited to, vinyl acetate,methyl methacrylate, methyl acrylate, styrene, alpha-methylstyrene,butyl acrylate, butyl methacrylate, amyl methacrylate, hexylmethacrylate, lauryl methacrylate, stearyl methacrylate, ethylhexylmethacrylate, crotyl methacrylate, cinnamyl methacrylate, oleylmethacrylate, ricinoleyl methacrylate, vinyl butyrate, vinyltert-butyrate, vinyl stearate or vinyl laurate.

The method of the invention advantaeously provides means to tailor thecomposition of the polymer that is formed at the surface of theparticulate material. In particular, the method provides means topolymerise specific or specialised monomers in strategic locationsthroughout the polymer. Such control over the polymerisation can beparticularly useful in preparing polymer encapsulated particulatematerials that are to be used in coating compositions such as paints.

Features of the invention which relate to the resulting polymercomposition that is formed at the surface of the particulate materialare discussed below with specific reference to an aqueous dispersion ofpolymer encapsulated pigment particles that are suitable for use as apigmented binder in waterborne paint formulations. However, it is to beunderstood that the general principles outlined below may be applied inother applications, such as in fillers, adhesives, primers and sealants,in which a polymer/particulate material composite formed in accordancewith the method may be used.

The modification of the polymer composition may be achieved by theselective polymerisation of specific or specialised monomers. Forexample, highly hydrophobic monomers such as 2,2,2-trifluoroethylmethacrylate (TFEM) may be polymerised at a stage during the method toprovide a highly hydrophobic surface region of the polymer. IntroducingTFEM to a polymer composition in this manner can promote stainresistance to a paint film when such particles are incorporated into apaint formulation. Alternatively, more polar monomers such asacrylamide, dimethyl amino ethyl methacrylate or ureido monomers may bepolymerised to provide a highly hydrophilic surface region of thepolymer. In this case, where the continuous liquid phase is hydrophilic,the hydrophilic portion of an amphipathic RAFT agent to be used in thepolymerisation may also comprise such monomers and thereby present ahighly hydrophilic polymer surface. Incorporation of such polar monomersat the surface of the polymer composition can assist in their adhesionto difficult surfaces when used in coating applications. In particular,as part of the hydrophilic end of an amphipathic RAFT agent, thelocation of these monomers at the surface of the polymer enables theirproperties as adhesion promoters to be maximised due to their ability tofreely interact with a substrate during film formation. Typically, suchspecific or specialised monomers are polymerised at relatively lowlevels, preferably at less than 10 wt % of the total monomer content,more preferably less than 5 wt % of the total monomer content, that ispolymerised to form polymer at the surface of the particulate materials.

The mode of polymerisation which operates in accordance with the methodof the invention also enables the internal composition of the polymerformed at the surface of the particulate material to be controlled. Inparticular, the composition of the internal region of the polymer can bevaried from that of the surface composition to provide an internalregion and an outer shell. In the simplest case, the polymer can beformed whereby a specific monomer is polymerised at one stage of theprocess and a different monomer is polymerised at a later stage to forma block copolymer. In this way, the particulate material may beencapsulated with a hard polymer with a soft film forming exterior, or asoft elastomeric polymer with a hard non-film forming skin. By the terms“hard” and “soft” polymer is meant polymers that are formed frommonomers where the homopolymer glass transition temperature (Tg) isabove and below room temperature (i.e. 25° C.), respectively. Suitablehard monomers include, but are not limited to, methyl methacrylate,t-butyl acrylate and methacrylate, and styrene. Suitable soft monomersinclude, but are not limited to, esters of acrylic acid such as ethyl,butyl and 2-ethyl hexyl acrylates.

The method of the invention might also provide an alternative route topreparing thermofusable powder paint (coating) materials. Thermofusablepowder paint materials are generally made by dispersing pigment intopolymer using a melt mixing process such as extrusion. The finalpigmented polymer mass formed from such a process is then mechanicallycomminuted to form a final powder coating composition. In use, suchthermofusable powder compositions are typically applied to a substrateby electrostatic spray techniques and subsequently fused onto thesubstrate by baking at high temperatures. Conventional thermofusablepowder coatings are typically based on crosslinkable thermofusablematerials to provide for coatings which are hard and have high levels ofchemical resistance and good adhesion to metal substrates. However, aproblem with conventional powder coatings is that the quality of pigmentdispersion afforded by extrusion is less than optimal and this generallyresults in the need for higher levels of pigmentation in order toachieve practical opacity.

The method of the invention provides means to prepare polymer havingpigment dispersed substantially uniformly therethrough, the attribute ofwhich makes it particularly suitable for use in preparing thermofusablepowder paint compositions. Such compositions can conveniently beprepared in the form of polymer particles which are of a tailored sizeand have pigment material dispersed substantially uniformlytherethrough, thereby allowing lower pigment loadings to be used. Inpreparing thermofusable powder paint compositions using the method ofthe invention, the continuous liquid phase will generally consistessentially of the one or more ethylenically unsaturated monomers andthis continuous liquid phase will be dispersed in a second continuousliquid phase as hereinbefore described. The monomers will typically beselected such that the resulting polymer is not film forming at roomtemperature. In particular, the monomers will typically be selected toprovide for a polymer that has a glass transition temperature above roomtemperature (i.e. about 25° C.) and preferably above 50° C. Afterpreparation, the dispersed polymer encapsulated particulate material maybe separated from the liquid by know techniques (e.g. filtration,centrifugation, freeze drying etc.) and dried for subsequent use.

The monomers may be selected to provide for a degree of crosslinking inthe applied thermofusable powder paint. However, it has been found thatthermofusable powder paints in accordance with the invention canadvantageously exhibit excellent adhesion to metal substrates withoutthe need to promote crosslinking in the applied coating. Wherecrosslinking is to be promoted in the applied coating, monomers may beselected which include functional groups that are capable of reactingwith complementary reactive groups from other monomers also incorporatedwithin the polymer. Such monomers will typically be chosen such thatthey react at the temperatures used to bake the thermofusable powderpaint after it has been applied to a substrate. Alternatively, thereactive functional monomers can be selected to only react with asuitable crosslinking agent added separately to the final thermofusablepowder paint formulation.

The invention may also be applied in biomedical applications, forexample in applications which use biocompatible polymer microparticlescontaining magnetic nanoparticles. Such microparticles can be deliveredintravascularly to perform various medically related functions. Theseapplications range from diagnostic functions such as MRI contrast agentsand cell targeting and separation to therapeutic technologies such asmagnetic drug targeting and targeted hyperthermia for the treatment ofcancer. These technologies rely on certain advantageous magneticcharacteristics of the polymer composite microparticles. For example,targeted hyperthermia therapy relies on magnetic characteristics beingoptimised to generate heat when the microparticles are exposed to a highfrequency magnetic field.

In view of the delicate nature of such in vivo applications, the need toprovide a high level of control over the final microparticle size andthe spatial arrangement of the constituent magnetic nanoparticlesincorporated within the polymer matrix is very important. In particular,the ability to uniformly distribute a high volume fraction of magneticnanoparticles into a polymer matrix is highly desirable. The method ofthe invention has been found to be well suited to preparing polymermicroparticles comprising magnetic nanoparticles uniformly distributedtherethrough.

The invention also provides a method of preparing a paint, thermofusablepowder paint, filler, adhesive, toner, liquid ink, primer, sealant,diagnostic product or therapeutic product comprising preparing adispersion of polymer encapsulated particulate material and/or a polymerhaving particulate material dispersed therethrough in accordance withthe invention, and combining the dispersion and/or polymer with one ormore formulation components.

Those skilled in the art will have an understanding of suitableformulation components that may be included in paints, thermofusablepowder paints, fillers, adhesives, toner, liquid ink, primers, sealants,diagnostic products or therapeutic products. Examples of suchformulation components include, but are not limited to, thickeners,antifungal agents, UV absorbers, extenders, bioactive reagents, andtinting agents.

The invention further provides a paint, thermofusable powder paint,filler, adhesive, toner, liquid ink, primer, sealant, diagnostic productor therapeutic product comprising a dispersion of polymer encapsulatedparticles and/or a polymer having particulate material dispersedtherethrough prepared in accordance with the invention.

Aqueous dispersions of polymer particles are used extensively inwaterborne products such as paints, adhesives, fillers, primers, liquidinks and sealants. Such products also typically comprise otherformulation components such as pigments, extenders, film forming aidsand other additives, all present at different levels and in differentcombinations. The use of pigments in such products is important not onlyin providing “hiding” power to the product but also to enable theproducts to be provided in a variety of colours.

Pigments have traditionally been incorporated in waterborne products byadding the pigments to a preformed aqueous dispersion of polymerparticles and dispersing them with the assistance of dispersing agents.Alternatively, pigments are dispersed with the aid of dispersing agentsin an initial stage to form what is termed a millbase, and then thismillbase is blended with a preformed aqueous dispersion of polymerparticles. The dispersion step requires high agitation speeds in orderto impart shear on the pigment particles. This dispersion step cansometimes be problematic because conventional aqueous dispersions ofpolymer particles are not always stable at the levels of shear exertedduring pigment dispersion.

In many applications where such pigmented products are used,agglomeration of pigment particles, in the product per se and alsoduring curing of the product, can adversely effect properties such asthe products gloss, scrub/stain resistance, flow, mechanical properties,opacity, colour and/or colour strength. Whilst being particularlydesirable, reducing or avoiding detrimental agglomeration of pigmentparticles in such products has to date been difficult to achieve usingconventional technology.

It has now been found that polymer encapsulated particulate materialhaving at least part of the encapsulating polymer formed under thecontrol of a RAFT agent can present a number of advantageous properties.For example, the polymer encapsulated particulate material can functionas a binder and a source of particulate material (e.g. in the form of apigment—a “pigmented binder”) in paint, filler, adhesive, primer, toner,liquid ink or sealant formulations. Providing the particulate materialin such an “embedded” form has been found to minimise, if not eliminate,problems such as pigment agglomeration in such products. By forming atleast part of the encapsulating polymer under the control of a RAFTagent, the particulate material can also be encapsulated in asubstantially uniform and continuous coating of polymer, or dispersedsubstantially uniformly throughout the encapsulating polymer.

For convenience only, the polymer encapsulated particulate material mayherein after be referred to as a “pigmented binder”. However, it is tobe understood that the pigment could readily be substituted for anyother suitable particulate material.

The present invention therefore further provides a compositioncomprising or consisting of discrete particles of polymer encapsulatedparticulate material, said particulate material being encapsulated in asubstantially uniform and continuous coating of a polymer which has atleast in part been formed under the control of a RAFT agent.

The present invention also provides a composition comprising orconsisting of discrete particles of polymer encapsulated particulatematerial, said discrete particles having the particulate materialsubstantially uniformly dispersed throughout the encapsulating polymer,wherein the encapsulating polymer has at least in part been formed underthe control of a RAFT agent, and wherein the discrete particles aresubstantially free of additional dispersant for the particulatematerial.

By being “substantially free of additional dispersant”, it will beappreciated from the foregoing that this relates to dispersant otherthan that which may be afforded by the RAFT agent.

By “discrete particles” is meant that polymer encapsulated particulatematerial within the composition may be separated into individualparticles. However, it will be appreciated that under certaincircumstances, for example where the encapsulating polymer has a low Tg,the particles may have a tendency to stick to each other. Nevertheless,the particles should still be discernible as discrete particles.

The composition may be in the form of a flowable powder, a slurry orpaste, or in the form of dispersion. In the case of a flowable powder,slurry or paste, the composition is preferably capable of being dilutedwith liquid to form a dispersion of the discrete particles. Aqueousdispersions of this type are suitable for use as a pigmented binder infor example waterbased paints, fillers, adhesives, primers, liquid inksand sealants.

The compositions of the invention may comprise or consist of pigmentparticles having a relatively thin (e.g. less than 10 nanometres)encapsulating polymer coating, which may be combined with conventionalwater based binders to afford paint formulations with a high applicationsolids content. The compositions may also be used as a primary pigmentedbinder, and even as a sole pigmented binder.

As a “primary” pigmented binder, it is to be understood that the binderwill be present in a given formulation in an amount greater than 50wt %,relative to the total mass of all binder used in that formulation.

In some formulations, it may be desirable to use the pigmented binder inan amount greater than about 60wt %, more preferably greater than about80wt %, most preferably greater than about 95wt %, still more preferablyas the sole pigmented binder (ie 100 wt. %), relative to the totalamount of all binder used in that formulation.

At least part of the encapsulating polymer of the polymer encapsulatedparticulate material in the compositions of the invention is formedunder the control of a RAFT agent. Preferably, the RAFT agent is asurface active or amphipathic RAFT agent as hereinbefore described. SuchRAFT agents can advantageously function as a stabiliser for the polymerencapsulated particulate material in a liquid dispersion, and/or promotesubstantially uniform distribution of particulate material throughoutthe encapsulating polymer.

In the form of liquid dispersion, the composition of polymerencapsulated particulate material is particularly suitable for use as apigmented binder in paint, filler, adhesive, primer, liquid ink orsealant formulations.

Accordingly, the present invention further provides liquid dispersion ofpolymer encapsulated particulate material, said particulate materialbeing encapsulated in a substantially uniform and continuous coating ofa polymer which has at least in part been formed under the control of aRAFT agent.

In this case, the RAFT agent can advantageously function as a stabiliserfor the dispersed polymer encapsulated particulate material. Preferably,the liquid dispersion is an aqueous dispersion.

The present invention also provides a liquid dispersion of polymerencapsulated particulate material, said polymer encapsulated particulatematerial having the particulate material substantially uniformlydispersed throughout the encapsulating polymer, wherein theencapsulating polymer has at least in part been formed under the controlof a RAFT agent, and wherein the polymer encapsulated particulatematerial is substantially free of additional dispersant for theparticulate material.

The present invention further provides a paint, filler, adhesive,primer, liquid ink or sealant formulation comprising a liquid dispersionof polymer encapsulated particulate material, said particulate materialbeing encapsulated in a substantially uniform and continuous coating ofa polymer which has at least in part been formed under the control of aRAFT agent.

The present invention also provides a paint, filler, adhesive, primer,liquid ink or sealant formulation comprising a liquid dispersion ofpolymer encapsulated particulate material having the particulatematerial substantially uniformly dispersed throughout the encapsulatingpolymer, wherein the encapsulating polymer has at least in part beenformed under the control of a RAFT agent, and wherein the polymerencapsulated particulate material is substantially free of additionaldispersant for the particulate material.

Preferably, the liquid dispersions are aqueous dispersions.

The method of the invention can be conveniently used to prepare thecompositions comprising polymer encapsulated particulate material.

The compositions of the invention are suitable for use as a pigmentedbinder in water-based decorative paint formulations. Decorative paintsare those that are typically applied to architectural features or thelike, and are most often used in households for application of bothinterior and exterior surfaces. As used herein, the term “decorativepaint(s)” is therefore intended to classify paints that do not need tobe subjected to high temperatures after their application to afford apolymeric film having the requisite physical and mechanical propertiesfor their intended application. Accordingly, such paints are to bedistinguished from those paints, such as industrial coatings, thatrequire high temperatures to enable the applied paint to form apolymeric film having the requisite physical and mechanical properties.

Paint formulations comprising the compositions of the invention canadvantageously afford films having improved properties such as improvedgloss, gloss retention, opacity, flow, scrub/stain resistance, colourand/or colour strength.

Poor gloss and flow of conventionally pigmented waterborne paints isoften associated with the premature flocculation of pigment during filmformation. Because both the binder and pigments are present as separateparticles, during film formation the pigment particles tend to becrowded into regions between binder particles which in turn restrictstheir mobility during the film forming process. This crowding effect oraggregation often results in a less uniform distribution of pigmentparticles within the film and can cause a reduction in gloss properties.In contrast, a pigmented film formed from a binder which is cast fromsolvent allows the pigment particles to move more freely until muchlater in the film forming process giving final films with improved glossand smoother surface appearance.

The compositions comprising or consisting of polymer encapsulatedparticulate material in accordance with the invention can advantageouslybe used to prepare waterborne coatings that can provide a surfaceappearance comparable to their solvent borne counterparts. The improvedsurface properties of such coatings are believed to result from theproblem of pigment aggregation during film formation being minimised, ifnot eliminated.

Paint film gloss is generally measured using instrument readings ofreflectivity taken at different angles from the vertical. Gloss readingsmeasured at a 20° angle describe the “depth of gloss” and are often usedto characterise low Pigment Volume Concentration (PVC) or gloss paints.Low PVC paints formulated using compositions of polymer encapsulatedparticulate material in accordance with the invention have been found toprovide 20° gloss readings which are superior to those measured forcomparative PVC conventional water-based paints. By way of example only,20° angle gloss readings of 1.5 times or more than those measured forequivalent PVC conventional water-based paints have been measured. Glossreadings at 60° and 85° of low PVC paints formulated using compositionsof the invention are also generally superior to those measured forcomparative PVC conventional water-based paints.

On visual examination of dried films formed from PVC paints formulatedusing compositions of the invention, distinction of image, a measure ofthe surface smoothness of the film evaluated by examination of astandard image and its reflection in the film, was also found to besuperior to that observed for comparative PVC conventional water-basedpaints.

Without wishing to be limited by theory, it is believed that theimproved gloss properties of paint films derived from paints inaccordance with the invention stem from the pigment particles being moreuniform in distribution throughout the paint film as a result of beingembedded in the encapsulating polymer during film formation.

The properties of opacity and hiding power depend on light absorption,light refractance and light reflectance of particles in a coating film.Only pigment and polymer interfaces are believed to contribute to theseproperties below the Critical Pigment Volume Concentration (CPVC, i.e.the PVC at which there is just sufficient binder to fill the intersticesbetween all the pigment and extender particles). Paint films derivedfrom paints in accordance with the invention have also been found todemonstrate superior light scattering properties. Thus, higher opacitycan advantageously be attained using comparatively less pigment.

Without wishing to be limited by theory, the polymer encapsulatedparticulate material is believed to provide a more uniform distributionof pigment throughout the paint film and thereby allow each pigmentparticle to give a maximum contribution to the total opacity and hidingpower of the film.

Flat (or Matt) waterbased paints are usually formulated at high pigmentloadings, often above the CPVC. At such high pigment loadings,properties such as opacity tend to be maximised, with added extenderparticles and air voids contributing to the hiding power of the film.However, properties such as mechanical strength, gloss and stainresistance tend to be adversely affected due to the porosity of theresultant paint films. Paint films derived from paints in accordancewith the invention have also been found to exhibit superior gloss,mechanical strength and stain resistance when formulated with arelatively high PVC (e.g. 72), compared to a conventional waterbasedpaint formulated to equivalent parameters of PVC, pigment to binderratio and solids.

Without wishing to be limited by theory, such improved properties ofpaint films derived from paints in accordance with the invention arebelieved to stem from the paint films being less porous compared to aconventional waterbased paint formulated to equivalent parameters ofPVC, pigment to binder ratio and solids.

The structural features of the paint films being less porous have alsobeen found to promote the retention of gloss of the paint film duringexterior weathering. Reduction in “glossiness” of paint films afterexposure to the elements, is due primarily to the effect of increasingpigment concentration near the film surface as the film binder degradesphotocatalytically. Paint gloss typically decreases with increased PVCat the surface. Such reduction in gloss is particularly severe as thePVC passes beyond the CPVC. Poor distribution of pigment in the paintfilm exacerbates this problem. Gloss retention, as a function ofexposure time, has been examined herein. Paint films derived from paintsin accordance with the invention have been found to exhibit a superiorresistance to gloss loss after more than 1,500 hours total exposure timein accelerated weathering experiments (relative to a conventionalwaterbased paint formulated to equivalent parameters of PVC, pigment tobinder ratio and solids), in particular with respect to the depth ofgloss visible. It is believed that such an advantageous property will beimparted to paint films derived from paints in accordance with theinvention formulated at any PVC.

The compositions of the invention can advantageously comprise or consistof polymer encapsulated particulate material where the particulatematerial is a coloured pigment, for example pthalocyanine blue pigment.In the form of an aqueous dispersion, such polymer encapsulated colouredpigment particles have been found to exhibit enhanced colouringcharacteristics compared with aqueous dispersions of polymer particlesin which the coloured pigment particles have been dispersed therethroughin a conventional manner.

Compositions comprising or consisting of polymer encapsulated colouredpigment particles can also be employed as tinters for conventionalpaints, fillers, adhesives, primers, liquid inks, toners, and sealants.In this case, the compositions are likely to be in the form of a freeflowing powder, a slurry or paste (i.e. a concentrate).

Rub off of coloured pigment from the surface of a dried paint film is aproblem frequently encountered in the coatings industry. This phenomenonis generally a result of either flooding or floating of pigment in thesystem, which occurs during the application of coloured waterborne latexbased paints. There are many factors that are known to influenceflooding and floating, for example the instability of the pigment andemulsion dispersion and/or the incompatibility of the pigment/pigmentpaste and the emulsion used. Paint films derived from paints inaccordance with the invention that are formulated with the polymerencapsulated coloured pigment particles have been found to exhibitlittle if no rub off. It is believed that such an advantageous propertywill be imparted to paint films derived from paints in accordance withthe invention formulated at any PVC.

When in the form of a free flowing powder, the compositions inaccordance with the invention can advantageously be used inthermofusable powder paint and novel “dry” coating formulations.

The compositions comprising or consisting of particulate materialssubstantially uniformally dispersed throughout the encapsulating polymerhave been found particularly suitable for use in thermofusable powderpaint formulations. Such compositions can advantageously simplify theability to provide coloured thermofused coatings. Conventionalthermofusable powder paint technology typically provides colouredformulations by extruding mixtures of coloured pigments with thethermofusable resin. However, by this technique uniform distribution ofthe pigment within the resin can be difficult to achieve and colourvariation within a batch and also relative to other batches can be aproblem. Thermofusable powder paint formulations in accordance with theinvention may be prepared using polymer encapsulated coloured pigmentand therefore can avoid the disadvantageous process step of extrudingpigment with a thermofusable resin. Thermofusable powder paintformulations in accordance with the invention have been found to provideuniform coloured thermofused coatings.

The compositions comprising or consisting of polymer encapsulatedparticulate material, wherein the particulate material is encapsulatedin a substantially uniform and continuous coating of polymer, areparticularly suited for use in “dry” coating compositions. Dry coatingcompositions have been used in the building and construction industryfor many years. Such compositions have generally been in the form of acement compositions comprising polymeric material to which water isadded to render the composition ready for use. However, due to the needto maintain optimal pigment dispersion in coating compositions such aspaints, conventional dry coating technology has to date been relativelyunsuccessful in being applied to coating compositions such as paints. Ithas now been found that liquid may be added to a free flowing powderform of the compositions in accordance with the invention to provide aliquid dispersion of the polymer encapsulated particulate material. Bybeing encapsulated in polymer, the particulate material has been foundto remain well dispersed not only in the liquid dispersion but also asthe liquid dispersion cures to form for example a paint film.Accordingly, such free flowing powder compositions may be convenientlyreferred to as a reconstitutable composition (for example areconstitutable paint) to which may be added a liquid such as water torender the composition ready for use. Reconsistutable paints of thistype may be conveniently packaged, for example in cardboard boxes, andstored for subsequent use.

Compositions in accordance with the invention that may be diluted toform a dispersion through the addition of liquid such as water, maycomprise other formulation components known to those skilled in the art.For example, the compositions may comprise a dispersant to facilitatedispersion of the polymer encapsulated particulate material within theliquid. However, compositions in accordance with the invention canadvantageously be used without the addition of a further dispersant as aresult of the RAFT agent used into form at least part of theencapsulated polymer also functioning as a stabiliser for the polymerencapsulated particulate material within the liquid. To facilitatedispersion of the polymer encapsulated particulate material within thediluting liquid, it may be preferable that the liquid is alkaline.Accordingly, it may be desirable to include in the composition, or thediluting liquid, a base for this purpose. Suitable bases include, butare not limited to, sodium or potassium hydroxide and ammonia (ammoniumhydroxide). Other suitable bases would be known to those skilled in theart.

To provide the compositions of the invention in the form of free flowingpowder, it has been found that the compositions should generally have asolids content of about 85 wt. % or more, preferably greater than about90 wt. %.

The free flowing powder compositions may be conveniently prepared usingthe method of the present invention. In this case, the resulting polymerencapsulated particulate material may be isolated using techniques wellknown in the art. Isolation of the polymer encapsulated particulatematerial might be by way of filtration, centrifugation and/orfreeze-drying. As indicated above, in order to obtain a free flowingpowder it will generally not be necessary to remove all liquid (forexample water) from the polymer encapsulated particulate material.

The polymer encapsulated particulate material used in the free flowingpowder compositions will generally comprise encapsulating polymer thatis sufficiently hard so that it can withstand the compressive forcesencountered as the polymer/particle composite is isolated and dried. By“hard” in this context it is meant that the Tg of the encapsulatingpolymer is sufficiently high to prevent or at least minimiseuncontrollable clumping or aggregation of the composite particles.Generally, the Tg of the encapsulating polymer will be greater than 0°C., more preferably greater than 10° C., more preferably greater than15° C.

The polymer matrix of the encapsulating polymer of the polymerencapsulated particulate material in the compositions of the inventionmay be conveniently tailored as hereinbefore described. For example, thepolymeric matrix of the encapsulating polymer may have a gradient and/ora layered structure as in a core/sheath (shell) type structure. As usedherein, the term “core” refers to an internal region or section of theencapsulating polymer, and the term “sheath” or “shell” refer to outerregions or sections of the encapsulating polymer. While the core/sheathterminology may imply that the encapsulating polymer is composed of twoseparate structural polymeric components it is to be understood that theencapsulating polymer may not have this exact structure and that thedistinction between the core and the sheath may not be as precise assuggested by this terminology.

It will be appreciated that where the free flowing powder compositionsare to be used as a reconstitutable coating or adhesive product, the Tgof the encapsulating polymer will need to be sufficiently low to enablecoalescence of the polymer encapsulated particulate material during thefilm forming or curing process. Generally, the Tg of the encapsulatingpolymer in this case will be less than about 70° C.

The present invention also provides a method of preparing a paint,filler, adhesive, liquid ink, primer, sealant, diagnostic product ortherapeutic product comprising forming a dispersion of polymerencapsulated particulate material by adding a liquid to the compositionsin accordance with the invention.

The invention further provides a paint, thermofusable powder paint,filler, adhesive, primer, toner, liquid ink, sealant, diagnostic productor therapeutic product comprising a composition in accordance with theinvention.

In considering a suitable RAFT agent for use in accordance with theinvention, the group represented by R¹ in formula (4) may be selectedsuch that it is either hydrophilic or hydrophobic in character. Due toR¹ being somewhat removed from the thiocarbonylthio group, its role inmodifying the reactivity of the RAFT agent becomes limited as nincreases. However, it is important that the group —(X)_(n)—R¹ offormula (4), and subsets thereof described herein (i.e. in formulas(14), (14a), and (14b)), is a free radical leaving group that is capableof re-initiating polymerisation.

The selection of Z is typically more important with respect to providingthe RAFT agent with the ability to gain control over the polymerisation.In selecting a Z group for compounds of formula (4) it is important thatsuch a group does not provide a leaving group that is a better leavinggroup in comparison with the —(X)_(n)—R¹ (or subset thereof) group offormula (4). By this limitation, monomer insertion preferentially occursbetween —(X)_(n)—R¹ (or subset thereof) and its nearest sulfur atom.This will of course not be relevant if the Z group is also an—(X)_(n)—R¹ group.

RAFT agents of formula (4) may be prepared by a number of methods.Preferably they are prepared by polymerising ethylenically unsaturatedmonomers under the control of a RAFT agent having the following generalformula (16):

where Z and R¹ are as previously defined.

In preparing surface active RAFT agents of general formula (4) from RAFTagents of general formula (16) it is important to bear in mind that theagent must also stabilise the particulate material in the continuousliquid phase. Compounds of formula (16) may also have some surfaceactivity, however they will generally not be able to stabilise theparticulate material in the continuous liquid phase. In order to achieveadequate stabilising properties, in the context of compounds of formula(4), compounds of formula (16) are subsequently reacted with appropriateethylenically unsaturated monomers. Having said this, when n=0 inconnection with formula (4), it is to be understood that such a compoundinherently possesses sufficient surface activity and can stabilise theparticulate material in the continuous liquid phase. In this case,formula (4) is equivalent to formula (16), and R¹ and Z provide adequatehydrophilic and hydrophobic properties, in their own right to afford asuitable surface active RAFT agent.

Ethylenically unsaturated monomers suitable for use in preparingcompounds of formula (4) can be any monomers that may be polymerised bya free radical process. Such monomers are typically chosen for theirhydrophilic or hydrophobic qualities.

Examples of suitable hydrophilic and hydrophobic ethylenicallyunsaturated monomers are the same as those hereinbefore described. Themonomers may also be selected for their ionisable or non-ionisablequalities. Examples of suitable ionisable ethylenically unsaturatedmonomers which have acid groups include, but are not limited to,methacrylic acid, acrylic acid, itaconic acid, p-styrene carboxylicacids, p-styrene sulfonic acids, vinyl sulfonic acid, vinyl phosphonicacid, ethacrylic acid, alpha-chloroacrylic acid, crotonic acid, fumaricacid, citraconic acid, mesaconic acid and maleic acid. Examples ofsuitable ionisable ethylenically unsaturated monomers which have basicgroups include, but are not limited to, 2-(dimethyl amino) ethyl andpropyl acrylates and methacrylates, and the corresponding3-(diethylamino) ethyl and propyl acrylates and methacrylates. Examplesof suitable non-ionisable hydrophilic ethylenically unsaturated monomersinclude, but are not limited to, hydroxy ethyl methacrylate, hydroxypropyl methacrylate, and hydroxy ethyl acrylate.

Polymerisation of the ethylenically unsaturated monomer to formcompounds of formula (4) may be conducted in either an aqueous solutionor an organic solvent, the choice of which is dictated primarily by thenature of the monomers to be polymerised. Polymerisation may also beconducted in the monomer itself.

Polymerisation of the monomers to form the RAFT agents of formula (4)will usually require initiation from a source of radicals. Initiatingsystems previously described are also suitable for this purpose.

A method for preparing a RAFT agent of formula (4) (or subsets thereof)wherein R¹ is hydrophilic might comprise first selecting a suitable RAFTagent. The selected RAFT agent is then combined with a thermalinitiator, solvent and hydrophilic monomer within a reaction vessel.Typically all reagents used are essentially free of dissolved oxygen andthe reaction solution is purged of any remaining oxygen by way of aninert gas, such as nitrogen, prior to polymerisation. The reaction issubsequently initiated by increasing the temperature of the solutionsuch that thermally induced homolytic scission of the initiator occurs.The polymerisation reaction then proceeds under control of the RAFTagent, thereby providing further hydrophilic character to thehydrophilic end of the RAFT agent through insertion of the hydrophilicmonomer. For compounds of formula (4) in which Z is sufficientlyhydrophobic, polymerisation of a second monomer may not be required. Forcompounds of formula (4) where Z is not sufficiently hydrophobic or forcompounds of formula (14), upon exhaustion of the hydrophilic monomer,hydrophobic monomer may be added to the solution immediately, or at alater stage if the intermediate product is isolated, and thepolymerisation continued under RAFT control to provide the blockcopolymer of formula (14). Where R¹ is intended to provide thehydrophobic properties to the RAFT agent, one skilled in the art willappreciate that the above method could be equally applied to prepare the“reverse” agent.

Generally, RAFT agents of formula (16) will not in their own rightpossess sufficient properties to function as stabiliser in accordancewith the method of the invention. Accordingly, when preparing a RAFTagent of formula (4), such as by a method described directly above,sufficient hydrophilic and/or hydrophobic monomers are generallypolymerised onto the RAFT agent to provide it with the requisiteproperties. At some point in time during the polymerisation of thehydrophilic and/or hydrophobic monomers, the RAFT agent will developsufficient surface activity. At this stage in the polymerisation the nowsurface active RAFT agent may be isolated and/or stored for subsequentuse. Alternatively, provided that the medium in which the surface activeRAFT agent has been prepared is suitable, solid particulate material cansimply be introduced to the reaction medium to thereby be stabilised andprovide for a dispersion of the particulate material throughout thecontinuous liquid phase. Additional monomer may then be introduced tothe continuous liquid phase in order to perform the method of theinvention.

It will be apparent to those skilled in the art that there are numerousways in which the method of the invention may be performed by firstforming a surface active RAFT agent in the continuous liquid phase (i.e.in situ). To further illustrate this aspect, one such approach isdescribed in more detail directly below.

The method of the invention might be used in a process for preparing anaqueous dispersion of polymer encapsulated titanium dioxide particlesfor use a binder material in paint formulations. This process mightinvolve selecting a water soluble RAFT agent of formula (16). Theselected RAFT agent may then be combined with a thermal initiator, wateras a solvent and hydrophilic monomer within a reaction vessel. Typicallyall reagents used will be essentially free of dissolved oxygen and thereaction solution is purged of any remaining oxygen by way of an inertgas, such as nitrogen, prior to polymerisation. The reaction may beinitiated by increasing the temperature of the solution such thatthermally induced homolytic scission of the initiator occurs. Thepolymerisation reaction then proceeds under control of the RAFT agent,thereby providing further hydrophilic character to the hydrophilic endof the RAFT agent through insertion of the hydrophilic monomer.

Upon exhaustion of the hydrophilic monomer, hydrophobic monomer may thenbe added to the solution and the polymerisation continued under RAFTcontrol to provide amphipathic character to the RAFT agent in a formsimilar to that described previously in point 6 relating to generalformula (14). Having attained the requisite surface active oramphipathic character of the RAFT agent, particulate titanium dioxidemay be introduced to the reaction medium whereby the now amphipathicRAFT agent can function to stabilise the particles and provide for adispersion of the titanium dioxide throughout the continuous aqueousphase. To ensure that adequate adsorption of the amphipathic RAFT agentto the titanium dioxide particles occurs, a small proportion ofionisable monomer such as acrylic acid may be copolymerised with thehydrophobic monomer used to afford the surface active or amphipathiccharacter to the RAFT agent.

Having provided a stable dispersion of the titanium dioxide particlesthroughout the continuous aqueous phase, hydrophobic monomer such asbutyl acrylate and methyl methacrylate may be introduced to the reactionmedium to be further polymerised under control of the RAFT agent andthereby form polymer at the surface of the titanium dioxide particles.The polymerisation may be continued to provide for a desired solidscontent, with the resulting aqueous dispersion of polymer encapsulatedtitanium dioxide particles being suitable for use as an opacified bindermaterial in paint formulations.

As an alternative to the method described directly above, a watersoluble RAFT agent of formula (16) might be used to prepare a surfaceactive RAFT agent having a less well defined block-like structure. Inthis case, rather than sequentially polymerising the hydrophilic monomerand then the hydrophobic monomer to provide an amphipathic RAFT agenthaving a structure of general formula (14), the hydrophobic andhydrophilic monomers may be added simultaneously at a selected ratio toafford surface active amphipathic RAFT agent of general formula (14a) ora surface active RAFT agent of general formula (14b). To afford astructure of the type represented by general formula (14a), the ratio ofhydrophobic to hydrophilic monomer will generally favour one of themonomers, for example as in a ratio of 1:2 or 1:3 and vice versa. Wherethe structure of the RAFT agent is to represent that of general formula(14b), the ratio of hydrophobic to hydrophilic monomer will generally beabout 1:1. As indicated above, variation of the ratio of hydrophilic tohydrophobic monomer polymerised in this way can be varied to best suitthe surface polarity characteristics of the particulate material. Havingformed a RAFT agent with the requisite surface activity, the method maybe continued as outlined above.

As mentioned above, suitable RAFT agents for the preparation of RAFTagents of formula (4) have the following general formula (16):

where R¹ and Z are as previously defined.

The effectiveness of a specific compound embraced by formula (16), as aRAFT agent, will depend on its transfer constant, which is determined bythe nature of the R¹ and Z groups, the monomer and the prevailingreaction conditions. These considerations are discussed above inrelation to RAFT agents of formula (4). With respect to the RAFT agentsof formula (16), such considerations are essentially the same. Inparticular, as groups R¹ and Z are carried through to the RAFT agent offormula (4), their selection is subject to similar considerations.However, due to closer proximity to the thiocarbonylthio group, the R¹group plays a significant role in the effectiveness of a specificcompound as a RAFT agent.

In selecting both R¹ and Z groups for RAFT agents of formula (16), thoseagents resulting from the combination of particularly preferred R¹ and Zgroups are also particularly preferred.

Most preferred RAFT agents include, but are not limited to, those agentsrepresented by the following general formulas 17 to 25:

wherein R³ is as previously defined.

When selecting a RAFT agent for use in aqueous environment, it ispreferable that it demonstrates hydrolytic stability. TrithiocarbonylRAFT agents are particularly preferred for use in an aqueousenvironment.

Where a dithiocarbonyl compound is used as a RAFT agent, it may be adithioester, a dithiocarbonate, a trithiocarbonate, a dithiocarbamate orthe like.

The invention will now be described with reference to the followingexamples which illustrate some preferred embodiments of the invention.However, it is to be understood that the particularity of the followingdescription is not to supersede the generality of the precedingdescription of the invention.

EXAMPLES Example 1 Encapsulation of TiO₂ Using poly(AA-co-BA-b-AM) MacroRAFT Agent

Part (a): Preparation of a poly{(butyl acrylate)_(m)-co-(acrylicacid)_(n)}-block-poly(acrylamide)_(t) Macro-RAFT Agent with RespectiveDegrees of Polymerization n≈3, m≈15 and t≈25 using2-amino-1-methyl-2-oxoethyl butyl trithiocarbonate.

A solution of 2-amino-1-methyl-2-oxoethyl butyl trithiocarbonate (0.86g, 3.6 mmol), 4,4′-azobis(4-cyanovaleric acid) (0.11 g, 0.4 mmol),acrylamide (6.42 g, 90.3 mmol) in dioxane (39.64 g) and water (15.33 g)was prepared in a 100 mL round bottom flask. This was stirredmagnetically and sparged with nitrogen for 15 minutes. The flask wasthen heated at 80° C. for 2 hrs. At the end of this period, butylacrylate (6.98 g, 54.4 mmol) and acrylic acid (0.81 g, 11.2 mmol) wereadded to the flask. The mixture was deoxygenated and heating wascontinued at 80° C. for a further 3 hours. The copolymer solution had20.5% solids.

Part (b): Poly(methyl methacrylate-co-butyl acrylate) Coating of TiO₂Particles (TR92) Using the Macro-RAFT Prepared in Part (a) as aStabiliser.

TiO₂ (Tioxide TR92 and supplied by HCA Colours Australia.) (10.23 g) wasmixed with water (2.18 g) and the macro RAFT agent solution (2.68 g,0.14 mmol) to form a white paste. More water (48.21 g) was mixed withthe paste, giving a white dispersion, which was further thoroughlydispersed using a Vibra-Cell Ultrasonic Processor (Sonics and Materials,Inc.) standard probe at 30% amplitude for 10 minutes. During thesonication process, the dispersion was stirred magnetically and cooledin a water bath. The white dispersion was transferred to a 100 ml roundflask and 4,4′-azobis(4-cyanovaleric acid) (0.028 g, 0.1 mmol) wasadded. The whole flask was immersed in an oil bath with temperaturesetting at 70° C. while a mixture of butyl acrylate (2.5 g, 19.5 mmol)and methyl methacrylate (2.5 g, 25.0 mmol) was fed into the flask at 2.5g/hr for 2 hours. After the monomer addition, the heating was continuedfor another 20 hours until full polymerization was achieved. Afterfiltering, the latex was white and stable, containing particles withsizes of about 370 nm (measured using dynamic laser lightscattering—HPPS, Malvern Instruments Ltd) and having 19.7% solids.

In order to facilitate observation of the particle coating bytransmission electron microscopy (TEM) the coating was crosslinked asfollows:

A solution of 2,2′-azobisisobutyronitrile (0.023 g, 0.14 mmol),methylmethacylate (2.03 g, 20.2 mmol) and ethyleneglycoldimethacrylate(0.21 g, 1.1 mmol) was mixed with 44.33 g of the latex, deoxygenated andheated at 80° C. for 1 hour to crosslink the polymer coatings on TiO₂particles to give a latex with 21.3% solids and an average particle sizeof 418 nm (measured using dynamic laser light scattering—HPPS, MalvernInstruments Ltd). Further TEM examination of the latex shows even andthick polymer coatings on the surface of the titanium dioxide particles.

Example 2 Encapsulation of TiO₂ Using poly(BA-b-AM) Macro RAFT Agent

Part (a): Preparation of a poly(butylacrylate)_(m)-block-poly(acrylamide)_(t) Macro-RAFT Agent withRespective Degrees of Polymerization m≈20 and t≈20 using2-amino-1-methyl-2-oxoethyl butyl trithiocarbonate.

A solution of 2-amino-1-methyl-2-oxoethyl butyl trithiocarbonate (0.85g, 3.6 mmol), 4,4′-azobis(4-cyanovaleric acid) (0.10 g, 0.4 mmol),acrylamide (5.06 g, 71.2 mmol) in dioxane (30.01 g) and water (15.33 g)was prepared in a 100 mL round bottom flask. This was stirredmagnetically and sparged with nitrogen for 15 minutes. The flask wasthen heated at 80° C. for 2 hours. At the end of this period, butylacrylate (9.15 g, 71.4 mmol) was added to the flask. The mixture wasdeoxygenated and heating was continued at 80° C. for a further 3 hours.The copolymer solution had 26.8% solids.

Part (b): Poly(methyl methacrylate-co-butyl acrylate) Coating of TiO₂Particles (TR92) Using the Macro-RAFT Prepared in Part (a) as aStabilizer.

TiO₂ powder (10.05 g) was well mixed with the macro RAFT agent solution(4.69 g, 0.27 mmol), then with dioxane (0.54 g) and finally water (10.10g) to form a white dispersion. This dispersion was further diluted withwater (42.36 g) and was subjected to ultra sonication using a Vibra-CellUltrasonic Processor (Sonics and Materials, Inc.) standard probe at 50%amplitude for 20 minutes to achieve a white dispersion. During thesonication the vessel was cooled in an ice bath, while stirringconstantly. After the sonication, the dispersed titanium dioxide wastransferred to a 100 ml round bottom flask containing4,4′-azobis(4-cyanovaleric acid) (0.028 g, 0.10 mmol), deoxygenated,sealed and immersed in an oil bath with temperature setting at 70° C. Asolution of butyl acrylate (2.5 g, 19.5 mmol, deoxygenated) and methylmethacrylate (2.5 g, 25.0 mmol, deoxygenated) was then fed into theflask using a syringe pump, over 2 hours at a rate of 2.5 g/hr. Afterthe monomer injection, the heating was continued for another 17 hoursuntil complete polymerization. The final latex was filtered to removecoagulum to yield a white latex with 16.8% solids and an averageparticle size of 496 nm (measured using dynamic laser lightscattering—HPPS, Malvern Instruments Ltd). To facilitate observation ofthe particle coating by TEM, the product was treated in a similarfashion to that described in Example 1, Part (b).

Example 3 Preparation of a Solid Polymer Matrix with MagneticNanoparticles Well Dispersed Therein

Part (a): Preparation of Diluted Aqueous Ferrofluid.

Magnetite nanoparticles were produced following the method of Massart(Preparation of aqueous magnetic liquids in alkaline and acidic media.IEEE Transactions on Magnetics, 1981. MAG-17(2): p. 1247-1248). Anaqueous mixture of ferric and ferrous chlorides was added to ammoniasolution. The resulting precipitate was isolated by centrifugation thenoxidized to maghemite by mixing with iron nitrate solution and heating.The precipitate was then washed in 2 molar nitric acid then finallypeptised by water to form a dilute aqueous ferrofluid (approximately1.8% solids). The aqueous ferrofluid thus obtained (188 g) was furtherdiluted with water (170 g) to obtain an aqueous ferrofluid ofapproximately 0.8% solids.

Part (b): Preparation of a poly(acrylic acid)-block-polystyreneMacro-RAFT Agent with Respective Degrees of Polymerisation n=5 and n=10Using: 2-{[(butylsulfanyl)carbonothioyl]sulfanyl} propanoic acid.

A solution of 2-{[(butylsulfanyl)carbonothioyl]sulfanyl} propanoic acid(2.55 g, 10.7 mmol), acrylic acid (3.86 g, 53.6 mmol) and4,4′-azobis(4-cyanovaleric acid) (0.3 g, 1.07 mmol) in dioxane (10 g) ina 50 ml round bottomed flask was stirred with an overhead stirrer, andheated to 60° C. in a nitrogen atmosphere for 2.5 hours. At the end ofthis period, styrene (10.96 g, 105 mmol), 4,4′-azobis(4-cyanovalericacid) (0.15 g, 0.54 mmol) and dioxane (16.4 g) was added to the flaskand heated continuously at 80° C. for a further 16 hours. The resultingcopolymer solution had approximately 40% solids.

Part (c): Preparation of a poly(acrylic acid)-block-polystyreneMacro-RAFT Agent with Respective Degrees of Polymerisation n=5 and n=20Using: 2-{[(butylsulfanyl)carbonothioyl]sulfanyl} propanoic acid.

A solution of 2-{[(butylsulfanyl)carbonothioyl]sulfanyl} propanoic acid(2.55 g, 10.7 mmol), acrylic acid (3.86 g, 53.6 mmol) and4,4′-azobis(4-cyanovaleric acid) (0.3 g, 1.07 mmol) in dioxane (10 g) ina 50 mL round bottomed flask was stirred with an overhead stirrer andheated to 60° C. in a nitrogen atmosphere for 2.5 hours. At the end ofthis period, (styrene 21.69 g, 208 mmol), 4,4′-azobis(4-cyanovalericacid) (0.15 g, 0.54 mmol) and dioxane (32.9 g) was added to the flaskand heating continued at 80° C. for a further 16 hours. The resultingcopolymer solution had approximately 40% solids.

Part (d): Preparation of Dry Fe₂O₃ Powder from the Aqueous Ferrofluid ofPart (a) and the Macro-RAFT Agent of Part (b).

Aqueous ammonia solution (10%, 2.25 g), followed by distilled water (83g) and ethanol (95%, 31 g) was added to the macro-RAFT solution frompart (b) to obtain a clear solution. Diluted aqueous ferrofluid of part(a) (358 g) was then fed drop wise into the above Marco-RAFT solutionover 160 min under mechanical agitation. Agitation was continued for afurther period of one hour after the dropwise addition was complete.Macro-RAFT agent of part (c) (3.85 g), aqueous ammonia (10%, 2.25 g),distilled water (83 g) and ethanol (95%, 31 g) was then added to thesuspension thus obtained. Approximately half of this suspension wasultrasonicated for 1 hour at 30% intensity (VCX 500, Sonics & MaterialsInc). The solid particles were then centrifuged out and dried in an ovenat 60° C.

Part (e): Preparation of a Styrene Based Ferrofluid from the Dry Powderof Part (d).

Powder from part (d) containing both Fe₂O₃ and macro-RAFT agent (2.0 g)together with styrene (5.0 g) and macro-RAFT agent solution from part(c) (0.4 g) was ground for 5 minutes using a mortar and pestle, Thecrude dispersion thus obtained was ultra sonicated for one hour at 30%intensity to obtain a styrene-based ferrofluid with an average particlediameter of 25 nm (Malvern HPPS). When this ferrofluid was exposed to anoscillating magnetic field of 100 kHz and 90 Oe it generated heat at arate of 9.6 W/g of Fe₂O₃.

Part (f): Preparation of Polystyrene Matrix Encapsulated Fe₂O₃ from theStyrene-Based Ferrofluid of Part (e).

To the entire sample from part (e) was added2,2′-azobis(2-methylpropionitrile) (0.013 g) and the reaction was heldat 75° C. in a nitrogen atmosphere for 15.5 hours. The resulting solidpolymer was ground to a powder which was found to contain 21.8% Fe₂O₃.The powder was dispersed in agar and when subjected to the same magneticfield as used in part (e) it generated 8.3 W/g of Fe₂O₃, indicatinglittle flocculation of the Fe₂O₃ particles during polymerisation.

Example 4 Encapsulation of TiO₂ Using poly(BA-co-AA) Macro-RAFT Agent

Part (a): Preparation of a poly(butyl acrylate-co-acrylic acid)Macro-RAFT Agent Containing an Average of 15 Monomer Units Per Chain ina Mole Ratio of 1:2 Using:2-{[(butylsulfanyl)carbonothioyl]sulfanyl}propanoic acid

A solution of 2-[(butylsulfanyl)carbonothioyl]sulfanyl propanoic acid(1.11 g, 4.6 mmol), 2,2′-azobisisobutyronitrile (0.07 g, 0.4 mmol),acrylic acid (3.39 g, 47.0 mmol) and butyl acrylate (3.16 g, 24.6 mmol)was prepared in dioxane (7.58 g) in a 50 mL round bottom flask. This wasstirred magnetically and sparged with nitrogen for 10 minutes. The flaskwas then heated to, and maintained at 70° C. for 3 hrs under constantstirring. The final copolymer solution was 54.8% solids.

Part (b): Poly(methyl methacrylate-co-butyl acrylate) Coating of TiO₂Pigment (TR92, Huntsman Corporation) Using Macro RAFT Agent from thisExample as a Stabilizer.

A solution containing macro RAFT (0.90 g, 0.3 mmol), water (50.06 g) andsodium hydroxide (0.05 g, 1.3 mmol) was prepared in a 100 mL beaker. Tothis solution, TiO₂ pigment (10.38 g) was added, mixed and thoroughlydispersed using a Vibra-Cell Ultrasonic Processor (Sonics and Materials,Inc.) standard probe set to 30% amplitude for 10 minutes. During thesonication process, the dispersion was stirred magnetically and cooledin a water bath. At the end of the dispersion, a small sample was takenand centrifuged at 14,000 rpm for 2 minutes using a mini centrifuge(Minispin Plus, Eppendorf) leaving a white deposit and a clear butslightly yellow supernatant, which indicated the presence of surplusmacro RAFT. To the pigment dispersion, a small extra amount of pigment(2.58 g) was added and again dispersed by sonication for another 10mins. The white dispersion (58.78 g) was transferred to a 100 mL roundflask containing 4,4′-azobis(4-cyanovaleric acid) (0.026 g, 0.1 mmol)and was deoxygenated by nitrogen sparging. The whole flask was immersedin an oil bath with a temperature setting of 70° C., while adeoxygenated mixture of butyl acrylate (1.39 g, 10.9 mmol) and methylmethacrylate (3.24 g, 32.4 mmol) was fed into the flask at 0.92 g/hrover 5 hours. After monomer addition was complete, the heating wascontinued for a further 11 hours after which time polymerization wasfound to be complete. After filtering, the latex was white and stable,containing particles about 365 nm in diameter (HPPS, Malvern InstrumentsLtd) The latex solids was 25.3%. The encapsulating polymer layers aroundTiO₂ particles was further increased by adding another deoxygenatedmixture of butyl acrylate (1.39 g, 10.9 mmol) and methyl methacrylate(3.24 g, 32.4 mmol) at 2.3 g/hr into the above latex (42.45 g) in thepresence of 4,4′-azobis(4-cyanovaleric acid) (0.025 g, 0.1 mmol) at 70°C. over 2 hrs. After the monomer addition was complete the temperaturewas maintained for a further 1 hour to complete polymerisation. Anaverage particle diameter of 493 nm was determined by dynamic laserlight scattering (HPPS, Malvern Instruments Ltd). The latex solids was31.7%. The polymer encapsulated TiO₂ prepared in this Example wereanalysed by TEM. A TEM image of the particles is shown in FIG. 1.

Example 5 Thermofusable Coating Containing Encapsulated TiO₂

Part (a): Preparation of a poly[butyl acrylate-co-N-(isobutoxymethyl)acrylamide-co-acrylic acid] Macro-RAFT Agent Containing an Average of 16Monomer Units Per Chain in a Mole Ratio of 2:1:5 Using:2-{[(butylsulfanyl)carbonothioyl]sulfanyl}propanoic acid.

A solution of 2-{[(butylsulfanyl)carbonothioyl]sulfanyl} propanoic acid(1.00 g, 4.2 mmol), 2,2′-azobisisobutyronitrile (0.04 g, 0.3 mmol),acrylic acid (3.11 g, 43.1 mmol), butyl acrylate (2.17 g, 16.9 mmol) andN-(isobutoxymethyl) acrylamide (1.34 g, 8.5 mmol) was prepared indioxane (7.50 g) in a 50 mL round bottom flask. This was stirredmagnetically and sparged with nitrogen for 10 minutes. The flask wasthen heated at 70° C. for 2 hours under constant stirring. The finalcopolymer solution was 43.8% solids.

Part (b): Poly(methyl methacrylate-co-N-(isobutoxymethyl)acrylamide-co-butyl acrylate) Coating of TiO₂ Pigment (TR92, HuntsmanCorporation) for Thermofusable Coating Using Macro RAFT Agent Preparedin Part (a) as a Stabilizer.

A solution containing macro RAFT agent (0.96 g, 0.3 mmol), water (52.19g) and sodium hydroxide (0.1 g, 2.5 mmol) was prepared in a 50 mlbeaker. To this solution, TiO₂ pigment (10.80 g) was added, mixed andthoroughly dispersed using a Vibra-Cell Ultrasonic Processor (Sonics andMaterials, Inc.) standard probe set to 30% amplitude for 10 minutes.During the sonication process, the dispersion was stirred magneticallyand cooled in a water bath. The white dispersion (56.22 g) wastransferred to a 100 ml round flask containing4,4′-azobis(4-cyanovaleric acid) (0.028 g, 0.1 mmol) and wasdeoxygenated by nitrogen sparging. The flask was immersed in an oil bathset to 70° C., while a deoxygenated mixture of butyl acrylate (2.10 g,16.4 mmol), methyl methacrylate (2.10 g, 21.0 mmol) andN-(isobutoxymethyl) acrylamide (0.42 g, 2.7 mmol) was fed into the flaskat 0.92 g/hr over 5 hours. After the monomer addition was complete, theheating was continued for another 16 hours after which polymerizationwas found to be complete. The resulting latex was white and stable,containing particles with an average diameter of about 413 nm (HPPS,Malvern Instruments Ltd). The latex solids was 23.7%. A further amountof 4,4′-azobis(4-cyanovaleric acid) (0.025 g, 0.1 mmol) was added to theresulting latex which was then deoxygenated. A further addition ofdeoxygenated monomer mixture containing butyl acrylate (2.10 g, 16.4mmol), methyl methacrylate (2.10 g, 21.0 mmol) and N-(isobutoxymethyl)acrylamide (0.42 g, 2.7 mmol) was then made at 2.3 g/hr over 2 hourswhile the vessel was maintained at 70° C. After the monomer addition wascomplete, the temperature was maintained for further hour to achievecomplete polymerisation. The latex particles had an average diameter of446 nm (HPPS, Malvern Instruments Ltd) and latex solids was 30.3%. Thelatex formed a white glossy film on a glass slide at room temperature.This film separated from the glass slide and disintegrated into smallpieces after washing with acetone. However, when the film was baked inan oven at 140° C. for 2 hours, it did not disintegrate in acetone ortetrahydrofuran.

Example 6 Encapsulation of TiO₂ Using poly(BA-co-AA) Macro RAFT Agent

Part (a): Preparation a poly(butyl acrylate-co-acrylic acid) Macro-RAFTAgent Containing an Average of 15 Monomer Units Per Chain in a MoleRatio of 1:2 Using: 2-{[(butylsulfanyl)carbonothioyl]sulfanyl}propanoicacid

A solution of 2-{[(butylsulfanyl)carbonothioyl]sulfanyl}propanoic acid(0.74 g, 3.1 mmol) and 2,2′-azobisisobutyronitrile (0.03 g, 0.16 mmol)was prepared in dioxane (4.90 g) in a 25 mL round bottom flask. This wasstirred magnetically and sparged with nitrogen for 10 minutes. The flaskwas then heated to and maintained at 70° C. under constant stirring.Butyl acrylate (2.18 g, 17.1 mmol) and acrylic acid (2.18 g, 30.3 mmol)was fed into the reaction at 4.36 g/hr for 1 hr. After which thereaction was left for a further hour, stirring at 70° C. The finalcopolymer solution was 50.0% solids.

Part (b): Poly(butyl acrylate-co-methyl methacrylate) Coating of TiO₂Pigment (TR92, Huntsman Corporation) Using Macro RAFT Agent Prepared inPart (a) as Stabilizer.

A solution containing macro RAFT agent (0.89 g, 0.3 mmol), water (50.01g) and sodium hydroxide (0.10 g, 2.5 mmol) was prepared in a 100 mLbeaker. To this solution, TiO₂ pigment (10.01 g) was added, mixed andthoroughly dispersed using a Vibra-Cell Ultrasonic Processor (Sonics andMaterials, Inc.) standard probe set to 30% amplitude for 10 minutes.During the sonication process, the dispersion was stirred magnetically.The white dispersion (51.99 g) was transferred to a 100 mL round flaskcontaining 4,4′-azobis(4-cyanovaleric acid) (0.02 g, 0.1 mmol) and wasdeoxygenated by nitrogen sparging. The flask was immersed in an oil bathwith temperature setting at 70° C. while a deoxygenated mixture of butylacrylate (1.34 g, 10.5 mmol) and methyl methacrylate (3.30 g, 33.0 mmol)was fed into the flask at 0.93 g/hr over 5 hours. After the monomeraddition was complete the heating was continued for further 15.5 hrsafter which time polymerization was found to be complete. The resultinglatex was white and stable, containing particles with an averagediameter of 407.6 nm (HPPS, Malvern Instruments Ltd). The latex solidswas 25.8%. A further amount of 4,4′-azobis(4-cyanovaleric acid) (0.03 g,0.1 mmol) was added to the resulting latex, which was then deoxygenated.A further addition of deoxygenated monomer mixture containing butylacrylate (1.48 g, 11.5 mmol) and methyl methacrylate (3.63 g, 36.3 mmol)was then made at 2.32 g/hr over 2.2 hours while the vessel wasmaintained at 70° C. After the second monomer addition was completedtemperature was maintained for a further 1.5 hours to achieve completepolymerisation. The final latex was white and stable, containingparticles with an average diameter of 407.6 nm (HPPS, MalvernInstruments Ltd). The latex particles had an average diameter of 496.6nm (HPPS, Malvern Instruments Ltd) and latex solids was 31.9%.

Example 7 Encapsulation of TiO₂ Using poly (BA-co-MAA) Macro RAFT Agent

Part (a): Preparation of poly(butyl acrylate-co-methacrylic acid)Macro-RAFT Agent Containing an Average of 15 Monomer Units per Chain ina Mole Ratio of 1:2 using:2-{[(butylsulfanyl)carbonothioyl]sulfanyl}propanoic acid.

A solution of 2-{[(butylsulfanyl)carbonothioyl]sulfanyl} propanoic acid(1.50 g, 6.3 mmol), 2,2′-azobisisobutyronitrile (0.06 g, 0.4 mmol),methacrylic acid (5.4 g, 63.1 mmol), butyl acrylate (4.36 g, 34.0 mmol)was prepared in dioxane (8.06 g) in a 50 mL round bottom flask. This wasstirred magnetically and sparged with nitrogen for 15 minutes. The flaskwas then heated at 60° C. for 3 hours under constant stirring. The finalcopolymer solution was 35.9% solids.

Part (b): Poly(butyl acrylate-co-methyl methacrylate) Coating of TiO₂Pigment (TR92, Huntsman Corporation) Using Macro RAFT Agent Prepared inPart (a) as Stabilizer.

A solution containing macro RAFT agent (0.85 g, 0.27 mmol), water (51.06g) and sodium hydroxide (0.11 g, 2.7 mmol) was prepared in a 100 mLbeaker. To this solution, TiO₂ pigment (10.06 g) was added, mixed andthoroughly dispersed using a Vibra-Cell Ultrasonic Processor (Sonics andMaterials, Inc.) standard probe set to 30% amplitude for 10 minutes.During the sonication process, the dispersion was stirred magnetically.The white dispersion (64.13 g) was transferred to a 100 mL round bottomflask containing 4,4′-azobis(4-cyanovaleric acid) (0.03 g, 0.1 mmol) andwas deoxygenated by nitrogen sparging. The flask was immersed in an oilbath set to 70° C. while a deoxygenated mixture of butyl acrylate (1.34g, 10.5 mmol) and methyl methacrylate (3.30 g, 33.0 mmol) was fed intothe flask at 0.93 g/hr over 5 hours. The resulting latex was white andstable, containing particles with an average diameter of 310.4 nm (HPPS,Malvern Instruments Ltd). The latex solids was 23.3%. A further amountof 4,4′-azobis(4-cyanovaleric acid) (0.02 g, 0.1 mmol) was added to theresulting latex, which was then deoxygenated. A further addition ofdeoxygenated monomer mixture containing butyl acrylate (1.34 g, 10.5mmol) and methyl methacrylate (3.30 g, 33.0 mmol) was then made at 2.32g/hr over 2 hours while the vessel was maintained at 70° C. After thesecond monomer addition was completed the temperature was maintained fora further hour to achieve complete polymerisation. The latex particleshad an average diameter of 366.6 nm (HPPS, Malvern Instruments Ltd) andsolids of 29.0%.

Example 8 Encapsulation of TiO₂ Using poly(BA-co-AA) Macro RAFT Agent

Part (a): Preparation of a poly(butyl acrylate-co-acrylic acid)Macro-RAFT Agent Containing an Average of 30 Monomer Units per Chain ina Mole Ratio of 1:2 Using:2-{[(butylsulfanyl)carbonothioyl]sulfanyl}propanoic acid

A solution of 2-{[(butylsulfanyl)carbonothioyl]sulfanyl}propanoic acid(0.40 g, 1.6 mmol), 2,2′-azobisisobutyronitrile (0.02 g, 0.1 mmol),acrylic acid (2.44 g, 33.8 mmol) and butyl acrylate (2.17 g, 16.9 mmol)was prepared in dioxane (10.04 g) in a 50 mL round bottom flask. Thiswas stirred magnetically and sparged with nitrogen for 10 minutes. Theflask was then heated at 70° C. under constant stirring for 2.5 hours.The final copolymer solution was 34.9% solids.

Poly(butyl acrylate-co-acrylic acid) Coating of TiO₂ Pigment (TR92,Huntsman Corporation) Using Macro RAFT Agent from Part (a) asStabilizer.

A solution containing macro RAFT from Part (a) (2.51 g, 0.3 mmol), water(50.94 g) and sodium hydroxide (0.06 g, 1.4 mmol) was prepared in a 100mL beaker. To this solution, TiO₂ pigment (11.26 g) was added, mixed andthoroughly dispersed using a Vibra-Cell Ultrasonic Processor (Sonics andMaterials, Inc.) standard probe set to 30% amplitude for 10 minutes.During the sonication process, the dispersion was stirred magneticallyand cooled in a water bath. At the end of the dispersion, a small samplewas taken and centrifuged at 14,000 rpm for 2 mins using a minicentrifuge (Minispin Plus, Eppendorf) revealing a white deposit and aclear but slightly yellow supernatant which indicated the presence ofsurplus macro RAFT. To the pigment dispersion, small extra amount ofpigment (1.64 g) was added and again dispersed by sonication for another10 mins. The white dispersion (56.72 g) was transferred to a 100 mLround bottom flask containing 4,4′-azobis(4-cyanovaleric acid) (0.029 g,0.1 mmol) and was deoxygenated by nitrogen sparging. The whole flask wasimmersed in an oil bath with a temperature setting of 70° C., while adeoxygenated mixture of butyl acrylate (1.39 g, 10.9 mmol) and acrylicacid (3.24 g, 32.4 mmol) was fed into the flask at 0.92 g/hr over 5hours. After monomer addition was complete, the temperature wasmaintained for a further 13.5 hours after which time polymerization wasfound to be complete. After filtering, the latex was white and stable,containing polymer encapsulated TiO₂ particles with 27.8% solids. Theencapsulating polymer layers around TiO₂ particles was increased furtherby adding another deoxygenated mixture of butyl acrylate (1.39 g, 10.9mmol) and acrylic acid (3.24 g, 32.4 mmol) at 2.3 g/hr into the abovelatex (48.46 g) in the presence of 4,4′-azobis(4-cyanovaleric acid)(0.028 g, 0.1 mmol) at 70° C. over 2 hours. After the monomer additionwas completed, the temperature was maintained for a further hour tocomplete polymerisation. An average particle diameter of 441 nm wasdetermined by dynamic laser light scattering (HPPS, Malvern InstrumentsLtd). The latex solids was 29.5%.

Example 9 Encapsulation of TiO₂ Using poly(BA-co-AA) Macro RAFT

Part (a): Preparation a poly(butyl acrylate-co-acrylic acid) Macro-RAFTAgent Containing an Average of 20 Monomer Units Per Chain in a MoleRatio of 1:1 Using: 2,2′-[(thioxomethylene)di(sulfanyl)]bis(propanoicacid).

A solution of 2,2′-[(thioxomethylene)di(sulfanyl)]bis(propanoic acid)(0.86 g, 3.4 mmol), 2,2′-azobisisobutyronitrile (0.03 g, 0.2 mmol),acrylic acid (2.41 g, 33.5 mmol), butyl acrylate (4.33 g, 33.8 mmol) wasprepared in dioxane (7.74 g) in a 50 mL round bottom flask. This wasstirred magnetically and sparged with nitrogen for 10 minutes. The flaskwas then heated to and maintained at 70° C. for 2 hours under constantstirring. The final copolymer solution was 56% solids.

Part (b): Polymethyl methacrylate-co-butyl acrylate) Coating of TiO₂Pigment (TR92, Huntsman Corporation) Using Macro RAFT Agent from Part(a) as Stabilizer.

A solution with pH 6 containing macro RAFT (1.25 g, 0.3 mmol), water(50.14 g) and sodium hydroxide (0.10 g, 2.4 mmol) was prepared in a 100mL beaker. To this solution, TiO₂ pigment (10.09 g) was added, mixed andwas further thoroughly dispersed using a Vibra-Cell Ultrasonic Processor(Sonics and Materials, Inc.) standard probe at 30% amplitude for 10minutes. During the sonication process, the dispersion was stirredmagnetically and cooled in a water bath. The white dispersion (56.87 g)was transferred to a 100 mL round bottom flask containing4,4′-azobis(4-cyanovaleric acid) (0.028 g, 0.1 mmol) and wasdeoxygenated by nitrogen sparging. The whole flask was immersed in anoil bath set to 70° C., while a deoxygenated mixture of butyl acrylate(1.39 g, 10.9 mmol) and methyl methacrylate (3.24 g, 32.4 mmol) was fedinto the flask at 0.92 g/hr over 5 hrs. After the monomer addition wascompleted, the heating was continued for a further 11 hours 30 minutes,after which time polymerization was found to be complete. The latex waswhite and stable, containing particles about 372 nm in diameter (HPPS,Malvern Instruments Ltd). Latex solids was 23.8%. The encapsulatingpolymer layers around TiO₂ particles was further increased by addinganother deoxygenated mixture of butyl acrylate (1.39 g, 10.9 mmol) andmethyl methacrylate (3.24 g, 32.4 mmol) at 2.3 g/hr into the above latexin the presence of 4,4′-azobis(4-cyanovaleric acid) (0.029 g, 0.1 mmol)at 70° C. over 2 hours. After monomer addition was complete thetemperature was maintained for a further 1 hour to effect fullpolymerisation. Examination by transmission electron microscopy showedindividually encapsulated TiO₂ particles. An average particle diameterof 464 nm was determined by dynamic laser light scattering (HPPS,Malvern Instruments Ltd). The latex solids was 30.1%.

Example 10 Encapsulation of TiO₂ Using poly(BA-co-MAA) Macro RAFT Agent

Part (a): Preparation a poly(butyl acrylate-co-methacrylic acid)Macro-RAFT Agent Containing an Average of 20 Monomer Units per Chain ina Mole Ratio of 1:1 Using:2,2′-[(thioxomethylene)di(sulfanyl)]bis(2-methylpropanoic acid).

A solution of 2,2′-[(thioxomethylene)di(sulfanyl)]bis(2-methylpropanoicacid) (0.10 g, 0.3 mmol), 2,2′-azobisisobutyronitrile (0.01 g, 0.04mmol), methacrylic acid (0.27 g, 3.1 mmol), butyl acrylate (0.44 g, 3.4mmol) in dioxane (1.52 g) was prepared in a 5 mL round bottom flask.This was stirred magnetically and sparged with nitrogen for 10 minutes.The flask was then heated at 70° C. for 3 hours under constant stirring.The final copolymer solution was 23.8% solids.

Part (b): Poly(methyl methacrylate-co-butyl acrylate) Coating of TiO₂Pigment (TR92, Huntsman Corporation) Using Macro RAFT Agent from Part(a) as Stabilizer.

A solution with pH 6.5 containing macro RAFT (1.00 g, 0.15 mmol), water(50.82 g) and sodium hydroxide (0.05 g, 1.3 mmol) was prepared in a 100mL beaker. To this solution, TiO₂ pigment (4.63 g) was added, mixed andthoroughly dispersed using a Vibra-Cell Ultrasonic Processor (Sonics andMaterials, Inc.) standard probe set to 30% amplitude for 10 minutes.During the sonication process, the dispersion was stirred magneticallyand cooled in a water bath. The white dispersion (47.11 g) wastransferred to a 100 ml round flask containing4,4′-azobis(4-cyanovaleric acid) (0.036 g, 0.1 mmol) and wasdeoxygenated by nitrogen sparging. The whole flask was immersed in anoil bath set at 70° C., while a deoxygenated mixture of butyl acrylate(1.39 g, 10.9 mmol) and methyl methacrylate (3.24 g, 32.4 mmol) was fedinto the flask at 0.92 g/hr over 5 hours. After the monomer addition wascompleted, the heating was continued for a further 11 hours, after whichtime polymerization was found to be complete. After filtering, the latexwas white and stable, containing particles about 415 nm in diameter(HPPS, Malvern Instruments Ltd). The latex solids was 12.1%.

Example 11 Polymer Coated Bismuth Vanadate Pigment Particles and aCoating Derived Therefrom

Part (a): Preparation of a poly{(butylacrylate)_(m)-co-(2-(dimethylamino)ethylmethacrylate)_(n)}-block-poly(acrylamide)_(t) Macro-RAFT Agent withRespective Degrees of Polymerization n≈5, m≈10 and t≈20 Using:2-{[(butylsulfanyl)carbonothioyl]sulfanyl}propanoic acid

A solution of 2-{[(butylsulfanyl)carbonothioyl]sulfanyl}propanoic acid(0.48 g, 2.0 mmol), 4,4′-azobis(4-cyanovaleric acid) (0.03 g, 0.1 mmol)acrylamide (2.95 g, 41.5 mmol) was prepared in dioxane (15.14 g) andwater (8.08 g) in a 50 mL round bottom flask. This was stirredmagnetically and sparged with nitrogen for 15 minutes. The flask wasthen heated to and maintained at 70° C. for 2 hours 30 minutes. At theend of this period, butyl acrylate (2.59 g, 20.2 mmol),2-(dimethylamino)ethyl methacrylate (1.58 g, 10.1 mmol) and anadditional amount of 4,4′-azobis(4-cyanovaleric acid) (0.03 g, 0.1 mmol)was added to the flask. The mixture was deoxygenated and heating wascontinued at 70° C. for a further 2hours. The copolymer solution was20.9% solids.

Part (b): Poly(methyl methacrylate-co-butyl acrylate) Coating of YellowBismuth Vanadate Pigment (Irgazin Yellow 2094, Ciba Specialty Chemicals)Using Macro RAFT from Part (a) as Stabilizer.

A solution containing macro RAFT (1.6 g, 0.11 mmol), water (51.10 g) wasprepared in a 100 ml beaker. To this solution, yellow pigment (5.06 g)was added, mixed and was dispersed using a Vibra-Cell UltrasonicProcessor (Sonics and Materials, Inc.) standard probe at 30% amplitudefor 10 minutes. During the sonication process, the dispersion wasstirred magnetically and cooled in a water bath. The pH of thedispersion was then adjusted to 4.4 and redispersed by ultrasonication.The yellow dispersion was transferred to a 100 ml round bottom flaskcontaining 4,4′-azobis(4-cyanovaleric acid) (0.0295 g, 0.1 mmol) and wasdeoxygenated by nitrogen sparging. The whole flask was immersed in anoil bath set of 70° C., while a deoxygenated mixture of butyl acrylate(0.70 g, 5.4 mmol) and methyl methacrylate (1.62 g, 16.2 mmol) was fedinto the flask at 0.92 g/hr over 2.5 hours. After monomer addition wascomplete, heating was continued for further 1 hour after which timepolymerization was found to be complete. After filtering, the latex wasyellow and stable, containing particles about 1.27 μm in diameter (HPPS,Malvern Instruments Ltd). The latex solids was 12.4%. The polymer coatedparticles prepared in this example were analysed by transmissionelectron microscopy (TEM).

Part (c): Waterborne Coloured Base Paint Formulated Using theEncapsulated Yellow Bismuth Vanadate Pigment Dispersion from Part (b).

Encapsulated yellow bismuth vanadate pigment dispersion from part (b)was formulated into a yellow base paint according to the followingmethod:

Conventional acrylic latex (ex Rohm and Haas) (79.729 g), PropyleneGlycol (2.141 g), Antifoam (0.589 g) and AMP-95 (0.321 g) were added toa high speed mixer with stirring. Biocide (0.086 g) was then added,followed by a pre-mix of Propylene Glycol (1.070 g) and Teric N40LP(0.214 g). Texanol (1.788 g) was then added in a pencil stream, and themixture stirred for 20 minutes. The following were then added to thereactor: Zinc Oxide (0.268 g) and the encapsulated yellow bismuthvanadate pigment dispersion (11.494 g). Natrosol Plus 330 (0.16 g) andpropylene glycol (1.070 g) were pre-mixed before adding to the reactor.The mixture was then stirred for 20 minutes prior to the addition ofAcrysol RM-2020 (1.070 g). Stirring was continued for 30 minutes. pH andviscosity were adjusted as required.

Paint Physical Properties:

Weight Solids: 40.54

Volume Solids: 37.03

WPL: 1.062

WPL Solids: 1.162

PVC: 0.52

P:B Ratio: 3:100

Part (d): Comparative Paint Example Showing the Impact Of Encapsulationon Base Paint Characteristics.

A conventional yellow base paint was prepared for comparative purposes,according to the following method:

Conventional acrylic latex (ex Rohm and Haas) (79.729 g), PropyleneGlycol (2.141 g), antifoam (0.589 g) and AMP-95 (0.321 g) were added toa high speed mixer with stirring. Proxel GXL (0.086 g) was then added,followed by a pre-mix of Propylene Glycol (1.070 g) and Teric N40LP(0.214 g). Texanol (1.788 g) was then added in a pencil stream, and themixture stirred for 20 minutes. The following were then added to thereactor: Zinc Oxide (0.268 g) and Conventional Yellow dispersion basedon Irgazin yellow 2094 ex Ciba Specialty Chemicals (11.494 g). NatrosolPlus 330 (0.16 g) and propylene glycol (1.070 g) were pre-mixed beforeadding to the reactor. The mixture was then stirred for 20 minutes priorto the addition of Acrysol RM-2020 (1.070 g). Stirring was continued for30 minutes. pH and viscosity were adjusted as required.

Paint Physical Properties:

Weight Solids: 39.54

Volume Solids: 35.90

WPL: 1.061

WPL Solids: 1.168

PVC: 0.73

P:B Ratio: 4:100

Results:

Films of the paint from Example 11(c) and the comparative example frompart (d) were cast onto Leneta white charts with a drawdown blade havinga 175 um gap and after drying for 24 hours were measured for gloss witha Dr Lange gloss meter. They were also evaluated visually for filmappearance:

Example 11 (c) Comparative Example Film Appearance Superior brillianceand Control depth of colour Gloss (°) 20 38.4 18 60 67.9 64.9 85 93.2 90

Optimisation of pigment particle size during paint manufacture normallyrequires reduction of particle agglomerates to smaller particle sizesthat are more efficient at light scattering. Pigment particle sizestrongly influences the tint strength or the depth of colour that can beachieved from a given quantity of pigment. The inclusion of pigmentagglomerates or flocculates acts to reduce the colour strength andbrightness of finished coatings. Some colour pigment types arenotoriously difficult to break down in terms of reducingagglomeration-inorganic yellows such as included in the present examplebeing one such type.

The colour strength of the paint from Example 11(c) and the comparativeexample was investigated. The paints from Example 11(c) and thecomparative example 11(d) were applied over a black and white substrateuntil the pattern was completely obliterated. The colour differencebetween the panels was then measured with a Macbeth 7000Aspectrophotometer and the colour difference coordinates calculated usingthe CIE1976 colour system. A total colour difference value of DE=1.97was obtained, with the film of the example showing enhanced yellowness(+1.62) and red tone (+1.09). An overall colour strength increase of 6%was observed.

No rub off of yellow pigment was seen herein when compared to thecomparative conventional example, which did experience light to mediumrub off of pigment, even at the low PVCs of formulation used.

Example 12 Preparation of a Solid Polyvinyl Acetate Matrix with MagneticNanoparticles Well Dispersed Therein

Part (a): Preparation of Diluted Aqueous Ferrofluid with Ph of 5.30.

Aqueous ferrofluid (˜3.7% solids) obtained as described in Example 3,Part (a) (53 g) was diluted with water (100 g) to obtain an aqueousferrofluid of approximately 1.3% solids. To this diluted ferrofluid,NaOH solution (0.3wt %) of 54 g was added over 7˜10 minutes under amechanical agitation of 800 rpm, adjusting the pH of the ferrofluid from1.86 to 5.30, after which 90 g of ethanol as added. A clear dilutedaqueous ferrofluid with pH 5.30 was obtained.

Part (b): Preparation of a poly (acrylic acid)-block-poly (vinylacetate) Macro-Xanthate Agent with Respective Degrees of Polymerisationn=10 and n=25 Using 2-[(ethoxycarbonothioyl)sulfanyl]succinic acid.

A solution of 2-[(ethoxycarbonothioyl)sulfanyl]succinic acid (1.45 g,6.09 mmol), acrylic acid (4.39 g, 60.9 mmol) and2,2′-azobisisobutyronitrile (AIBN, 0.11 g, 0.609 mmol) in dioxane (8.9g) in a 100 mL round bottomed flask was stirred with an magnetic stirrerand heated to 65° C. in a nitrogen atmosphere for 3 hours. At the end ofthis period, vinyl acetate 12.93 g, 150 mmol), AIBN (0.05 g, 0.3 mmol)and dioxane (19.46 g) was added to the flask and heating continued at80° C. for a further 16 hours. The resulting copolymer solution wasapproximately 46% solids.

Part (c): Preparation of Dry Fe₂O₃ Powder from the Aqueous Ferrofluid ofExample 12, Part (a) and the Macro-Xanthate Agent of Example 12, Part(b).

Aqueous sodium hydroxide solution (0.3%, 15.6 g), followed by distilledwater (3.8 g) and ethanol (95%, 8.9 g) was added to 2.72 g themacro-xanthate solution from Example 12, Part (b) to obtain a clearsolution. Diluted aqueous ferrofluid (pH=5.3) of Example 12, Part (a)(297 g) was then fed quickly into the above Marco-RAFT solution withinone min under mechanical agitation of 800 rpm. Agitation was continuedfor a further period of one hour. The suspension thus obtained wasultrasonicated for 10 minutes at 30% intensity (VCX 500, Sonics &Materials Inc). Another 15 g NaOH (0.3%) was added to adjust to pH to6.24, followed by 10 min. of sonication, addition of HCl (16wt %, 0.08g) to adjust the pH to 6.24, another 40 min. of sonication, and againaddition of HCl (16wt %, 0.48 g) to adjust the pH to 2.4. Finally thesupernate water of the above mixture was removed, NaOH (0.3%, 3.22 g)was added to the sediment to increase the pH back to 5.15. The finalsediment was then dried in an oven at 60° C., and 2.14 g of dry powderwas obtained.

Part (d): Preparation of a Styrene Based Ferrofluid from the Dry Powderof Example 12, Part (c).

Powder from Example 12, Part (c) containing both Fe₂O₃ andmacro-xanthate agent (2.14 g) together with vinyl acetate (6.0 g) andmacro-xanthate agent solution from Example 1b (0.63 g) was mixedtogether. The crude dispersion thus obtained was ultra sonicated for twohours at 30% intensity to obtain a vinyl acetate-based ferrofluid. Thisferrofluid was found to contain 28.5% of Fe₂O₃, and when exposed to anoscillating magnetic field of 100 kHz and 90 Oe it generated heat at arate of 10.7 W/g of Fe₂O₃, which is 57.2% of the original aqueousferrofluids.

Part (e): Preparation of poly (vinyl acetate) Matrix Encapsulated Fe₂O₃from the Vinyl Acetate-Based Ferrofluid of Example 12, Part (d).

To the 4.9 g of the sample from Example 12, Part (d) was added the AIBN(0.0267 g). The above mixture was then mixed on a vortex mixer 2 min.The bulk polymerization was then carried out in a silicane oil bath of75° C. for 14 hours. The final solid polymer was obtained. And it wasfound to contain 35.1% Fe₂O₃. When the powder was dispersed in agar andsubjected to the same magnetic field as used in Example 12, Part (d) itgenerated 8.4 W/g of Fe₂O₃.

Example 13 Polymer Coated Phthalocyanine Blue Pigment Particles and aCoating Derived Therefrom

Part (a): Preparation of a poly(butyl acrylate-co-acrylic acid)Macro-RAFT Agent Containing an Average of 10 Monomer Units Per Chain ina Mole Ratio of 1:1 Using:2-{[(butylsulfanyl)carbonothioyl]sulfanyl}propanoic acid

A solution of 2-{[(butylsulfanyl)carbonothioyl]sulfanyl}propanoic acid(1.44 g, 6.0 mmol), 2,2′-azobisisobutyronitrile (0.06 g, 0.4 mmol),acrylic acid (2.26 g, 31.4 mmol), butyl acrylate (3.93 g, 30.7 mmol) wasprepared in dioxane (7.78 g) in a 50 mL round bottom flask. This wasstirred magnetically and sparged with nitrogen for 10 minutes. The flaskwas then heated at 70° C. for 2 hours 30 minutes under constantstirring. The final copolymer solution was 50.9% solids.

Part (b) Poly(methyl methacrylate-co-butyl acrylate) Coating ofPhthalocyanine Blue Pigment (Heliogen Blue L6900, BASF) Using Macro RAFTfrom Part (a) as a Stabilizer.

A solution containing macro RAFT (0.73 g, 0.3 mmol), ethylene glycol(19.08 g) and methanol (3.10 g) was prepared in a 50 mL beaker. To thissolution, water (10.49 g) and then sodium hydroxide (0.06 g, 1.48 mmol)was added, mixed and sonicated in a sonic bath for 2 minutes. Thesolution was transferred to a water-jacketed milling vessel (Dispermat™AE 3C laboratory dissolver fitted with an APS 250 milling system,VMA-Getzmann) containing phthalocyanine blue pigment (5.01 g) and 1 mmin diameter glass beads (101 g). The bath jacket temperature wasmaintained at 20° C. The milling was initially at 1000 rpm for 60minutes to produce a viscous blue dispersion. Then, more water (20.00 g)and glass beads (50 g) were added into the milling vessel and themilling speed was raised to 6000 rpm for 60 minutes. At the end of themilling, another portion of water (70.17 g) was mixed with the pigmentdispersion. Foam and glass beads were then separated from the dispersionusing a plastic mesh while large pigment particles were removed bycentrifugation at 2000 rpm for 5 minutes (MSE MK2 centrifuge, ThomasOptical & Scientific Co Pty Ltd). The pigment dispersion (50.64 g) wastransferred into a 100 mL round bottom flask containing4,4′-azobis(4-cyanovaleric acid) (0.025 g, 0.1 mmol). The flask wassealed, sparged with nitrogen for 15 minutes, placed in an oil bathmaintained at 70° C. and stirred magnetically. A deoxygenated solutionof butyl acrylate (1.39 g, 10.9 mmol) and methyl methacrylate (3.24 g,32.4 mmol) was injected into the flask at a rate of 1 ml/hour for 5hours Addition commenced 10 minutes after completion of the initialsparge. Bath temperature was maintained at 70° C. for a further 11 hoursafter monomer injection was complete to achieve full polymerization.After filtering, a stable blue latex was obtained with a solids contentof 9.2%. The latex had an average particle diameter of 181 nm asmeasured using dynamic laser light scattering (HPPS, Malvern InstrumentsLtd). Transmission electron microscopy showed that the latex containedindividually encapsulated blue pigment particles (see FIG. 2). Theability of the method of the invention to form polymer at the surface ofhigh aspect ratio small particles is shown in FIG. 3. In this Figure,the polymer encapsulated phthalocyanine blue pigment having a needleshape was prepared in a similar manner to the current Example.

Part (c) Poly(methyl methacrylate-co-butyl acrylate) Coating ofPhthalocyanine Blue Pigment (Heliogen Blue L7081D, BASF) Using MacroRAFT from Part (a) as a Stabilizer.

Generally the same method was applied as for dispersion andencapsulation of Heliogen Blue L 6900 in part (b) apart from a slightvariation in the milling step. As Heliogen Blue 7081D is more readilydispersed than Heliogen Blue L 6900, the millbase was mixed at 2000 rpmsfor 30 minutes and then after the addition of the 20 g of let downwater, mixed a further 30 minutes at 4500 rpms.

Part (d): Waterborne Coloured Base Paint Formulated Using theEncapsulated Phthalocyanine Blue Pigment (Heliogen Blue L7081D, BASF)Dispersion from Part (c).

Encapsulated pthalocyanine blue pigment dispersion from part (c) wasformulated into a blue base paint according to the following method:

Conventional acrylic latex (ex Rohm and Haas) (73.388 g), antifoam(0.482 g) and conventional titanium dioxide dispersion (using Tiona RCL595 ex Millenium Inorganics) (6.490 g) were added to a high speed mixerwith stirring. These were followed by addition of water (10.019 g) andbiocide (0.083 g). A pre-mix of Propylene Glycol (2.255 g), Teric 164(0.159 g) and Teric N40LP (0.148 g) was subsequently added withstirring. Texanol (1.854 g) was then added in a pencil stream, and themixture stirred for 30 minutes. Natrosol Plus 330 (0.352 g) andpropylene glycol (1.131 g) were pre-mixed before adding to the reactor.Acrysol RM-2020 (2.195 g) was then added as stirring continued. Thedispersion of Example 11(c) (1.444 g) was added to the mixture andstirring continued for 60 minutes.

Paint Physical Properties:

Weight Solids: 41.80

Volume Solids: 38.56

WPL: 1.069

WPL Solids: 1.159

PVC: 0.96

P:B Ratio: 3:100

Part (e): Comparative Paint Example Showing the Impact of Encapsulationon Base Paint Characteristics.

A conventional blue base paint was prepared for comparative purposes,according to the method given above, however Heliogen blue L7081Ddispersed by conventional means (Luconyl dispersion ex BASF: contains30% pigment, 0.167 g) and water (1.277 g) replaced the amount ofdispersion from Example 13(c) added. This ensured an equivalent amountof colour pigment (g/L) was included in each formulation.

Paint Physical Properties:

Weight Solids: 41.72

Volume Solids: 38.44

WPL: 1.068

WPL Solids: 1.159

PVC: 0.97

P:B Ratio: 3:100

Results:

Sufficient coats of each of the exemplified and conventional base paintsto give black and white coverage, were applied to Leneta 5DX cards. Thecolour difference between the cards was measured using a Macbeth 7000Aspectrophotometer and the colour difference evaluated using the CIE1976L* a* b* colour space.

Films cast from the aqueous dispersion of polymer encapsulatedpthalocyanine blue particles exhibited enhanced colour strength,approximately 67% (K/S) higher, showing a lightness difference of 5.25(darker, deeper blue film) and a total colour difference of 6.13 (CIE)when compared to the comparative example from part (e). The enhancedblueness of the film is displayed numerically in the table below. Valuesof colour difference for the exemplified paint are quoted against thecomparative example from part (e) taken as standard.

Colour Strength (K/S DL DA DB % increase) (+L −D) (+R −G) (+Y −B) DE(CIE) Example 67.5 −5.25 1.48 −2.74 6.13 13(e)

Visual observation of the dried films of the coatings of the inventionas described above, showed apparent gloss, brilliance, clarity as wellas depth of colour to be vastly superior to the equivalent comparativeexample. Measured values of gloss matched the results arrived at by eye.Films of the paint from Example 13 (d) and the comparative example 13(e) were cast onto Leneta white charts with a drawdown blade having a175 um gap and after drying for 24 hours were measured for gloss with aDr Lange gloss meter. The results for 20⁰ gloss as measured indicate thedepth of gloss observed.

Gloss (°) Example 13 (d) Comparative Example 13(e) 20 43.0 27.3 60 80.776.6 85 95.7 92.4

As shown in FIG. 4, scattering and absorption coefficients over a rangeof wavelengths in the visible region were measured as another means toenable changes in efficiency of the pigment, when treated by the methodof the invention, to be displayed.

When evaluated over Leneta cards the films, as described, possessedexcellent colour strength. Through further formulation, it wasdiscovered that the colour strength achieved from aqueous dispersions ofpolymer encapsulated pthalocyanine blue particles in a blue baseformulation, could only be matched in a comparative conventional systemif the loading of pthalocyanine blue pigment was increased byapproximately 160% in the latter i.e. 2.6 times more pigment needed tobe included in the conventional comparative example (as included in thepaint derived in part (d)) to achieve the same colour strength asachieved through use of dispersions formulated via the method of thepresent invention. More efficient utilisation of the coloured pigment ofaround 60-70% has thus been evidenced in this example.

As discussed under example 11, rub off of coloured pigment from thesurface of dried paint films is a problem frequently encountered in thecoatings industry. No rub off of blue pigment was seen here whencompared to the conventional examples which both experienced observedrub off of pigment, even at such relatively low PVCs of formulation.This is an advantageous finding and is expected to follow for basecoatings formulated to any PVC.

Part (f): Exemplification of the Use of Encapsulated Pigment Dispersionsas Tinters of Conventional Paint Systems.

It has been found that latexes formed from the method of the inventionmay also be employed as tinters of conventional waterborne coatingsystems.

A dispersion of pthalocyanine blue as described in part (c) was used totint a conventional white paint of PVC 15 (comparative example 1 fromExample 20). Through experimentation it was discovered that only half asmuch of the encapsulated pthalocyanine blue pigment dispersion needed tobe added to give colour strength equivalent to that of the conventionalpthalocyanine blue pigment dispersion when added as a tinter. To getapproximately equivalent colour strength, 25.16 g of the dispersion frompart (c) (contains 11.52% solids, 3.5% pigment) or 25.16 g of theconventional dispersion (diluted to 11.5% solids, contains 7.2% pigment)was added to 250 ml of the conventional white paint (comparative example1 from Example 20).

The dispersion of part (c) was also used in tinting a waterborne low PVCpaint formulated using the encapsulated TiO₂ dispersion of the presentinvention (as from Example 20(c)). The improvement in colour strengthachieved was even greater therein.

Films of the tinted paints from this example were cast onto Leneta whitecharts with a drawdown blade having a 175 um gap and after drying for 24hours were measured for gloss with a Dr Lange gloss meter:

Conventional paint Paint from Conventional paint tinted usingencapsulated TiO₂ tinted using conventional (Example 20(c) tinted Glossdispersion from Part pigment using dispersion from (°) (c) dispersionPart (c) 20 20.6 16.4 38.4 60 61.5 61.3 67.9 85 88.9 88.2 93.2

Example 14 Themofusable Powder Coating

Part (a): Preparation of a poly(butyl acrylate-co-acrylic acid)Macro-RAFT Agent Containing an Average of 20 Monomer Units per Chain ina Mole Ratio of 3:1 Using2-{[(butylsulfanyl)carbonothioyl]sulfanyl}propanoic acid.

A solution of 2-{[(butylsulfanyl)carbonothioyl]sulfanyl}propanoic acid(0.71 g, 3.0 mmol), 2,2′-azobisisobutyronitrile (0.04 g, 0.2 mmol),acrylic acid (1.10 g, 15.2 mmol), butyl acrylate (5.73 g, 44.7 mmol) wasprepared in dioxane (9.13 g) in a 50 mL round bottom flask. This wasstirred magnetically and sparged with nitrogen for 10 minutes. The flaskwas then heated at 70° C. for 2 hours 30 minutes under constantstirring. The final copolymer solution was 41.7% solids.

Part (b): Preparation of Thermofusable Powder Coating Particles UsingMacro RAFT Agent Prepared in Part (a).

Titanium dioxide (20.1 g) was dispersed in a solution of butyl acrylate(14.1 g, 0.11 moles), methyl methacrylate (26.2 g, 0.26 moles), macroRAFT agent (3.1 g, 0.5 mmol),2-{[(butylsulfanyl)carbonothioyl]sulfanyl}propanoic acid (0.40 g, 1.7mmol) by mixing. To this dispersion, Resiflow PL200A (0.82 g) andhydrogenated castor oil (HCO, 0.87 g) was added and the dispersion wasfurther dispersed using a Vibra-Cell Ultrasonic Processor (Sonics andMaterials, Inc.) standard probe at 30% amplitude for 5 minutes. Aftersonication, the white dispersion was transferred to a 100 mL roundbottom flask containing 2,2′-azobisisobutyronitrile (0.1 g, 0.6 mmol)and was then deoxygenated by nitrogen sparging for 10 minutes. The flaskwas immersed in a temperature controlled oil bath for 1 hour at 70° C.to receive a slightly viscous white dispersion which contained 54%solids. To this dispersion, a solution of butyl acrylate (7.61 g, 59.4mmol), methyl methacrylate (14.14 g, 0.14 moles) was added. The diluteddispersion (30.87 g) was mixed with 2,2′-azobisisobutyronitrile (0.19 g,1.2 mmol) in a 100 mL beaker and was then redispersed in a polyvinylalcohol solution (49.98 g, 2.5%, 80000-100000 g/mole, 88% hydrolysed) bya overhead mixer spinning at 1200 rpm over 5 mins. The suspension wasquickly transferred to a 100 mL round bottom flask containing sodiumnitrite (0.0064 g, 0.1 mmol) which was in turn sealed and deoxygenatedby nitrogen sparging for 10 minutes. The polymerisation was carried outin a temperature controlled oil bath for 16 hours at 70° C. while wasconstantly magnetically stirred. At the end of the polymerisation, thelatex was filtered to remove coagulations and was centrifuged and washedfour times with distilled water to receive a wet powder which containedspherical particles with an estimated average particle size of 25microns (Carl Zeiss optical microscope). A solution of Primid XLS52crosslinker (0.29 g) and water (4.04 g) was mixed with the wet powderand the whole sample was let to be air dried overnight forming a drycake which was in turn broken up by grinding using a mortar and a pestleand was sieved using a 125 micron sieve. The final product formed a hardglossy white film on a glass slide after baking at 200° C. for10minutes.

Example 15 Thermofusable Powder Coating

Part (a): Preparation of Thermofusable Powder Coating Particles UsingMacro RAFT Agent Prepared in Example 14, Part (a) and Dodecyl Thiol asChain Transfer Agent.

Titanium dioxide (20.34 g) was dispersed in a solution of butyl acrylate(10.32 g, 0.08 moles), methyl methacrylate (30.95 g, 0.31 moles) andmacro RAFT agent from Example 14, Part (a) (3.47 g, 0.6 mmol) by mixing.To this dispersion, Resiflow PL200A (0.81 g) was added and thedispersion was further dispersed using a Vibra-Cell Ultrasonic Processor(Sonics and Materials, Inc.) standard probe at 30% amplitude for 5minutes. After sonication, the white dispersion was transferred to a 100mL round bottom flask containing 2,2′-azobisisobutyronitrile (0.10 g,0.6 mmol), dodecyl thiol (0.55 g, 2.7 mmol) and hydrogenated castor oil(HCO, 0.86 g) and was sealed then deoxygenated by nitrogen sparging for10 minutes. The flask was immersed in a temperature controlled oil bathfor 1 hour at 70° C. to receive a slightly viscous white dispersionwhich contained 55.5% solids. To this dispersion, a solution of butylacrylate (5.11 g, 39.8 mmol), methyl methacrylate (15.32 g, 0.15 moles)was added. The diluted dispersion (28.35 g) was preheated to 70° C.,then mixed with 2,2′-azobisisobutyronitrile (0.20 g, 1.2 mmol) in a 100mL beaker and was then redispersed in a preheated (90° C.) polyvinylalcohol solution (64.23 g, 2.5%, 80000-100000 g/mole, 88% hydrolysed) bya overhead mixer spinning at 1500 rpm over 5 minutes. The suspension wasquickly transferred to a 100 mL round bottom flask containing sodiumnitrite (0.0062 g, 0.1 mmol), which was in turn sealed and deoxygenatedby nitrogen sparging for 10 minutes. The polymerisation was carried outin a temperature controlled oil bath for 4 hours at 90° C., while wasconstantly stirred magnetically. At the end of the polymerisation, thelatex was filtered to remove coagulations and was centrifuged and washedsix times with distilled water to receive a wet powder which containedspherical particles with an estimated average particle size of 25microns (Carl Zeiss optical microscope). A solution of Primid XLS52crosslinker (0.51 g) and water (2.07 g) was mixed with the wet powderand the whole sample was let to be air dried overnight forming a drycake which was in turn broken up by grinding using a mortar and a pestleand was sieved using a 125 micron sieve. The final product formed a hardand glossy white film on a glass slide at 200° C. after 10 minutes.

Example 16 Thermofusable Powder Coating Based On:2-{[(dodecylsulfanyl)carbonothioyl]sulfanyl}propanoic acid

Part (a): Preparation of a poly(butyl acrylate-co-acrylic acid)Macro-RAFT Agent Containing an Average of 20 Monomer Units per Chain ina Mole Ratio of 3:1 Using:2-{[(dodecylsulfanyl)carbonothioyl]sulfanyl}propanoic acid.

A solution of 2-{[(dodecylsulfanyl)carbonothioyl]sulfanyl}propanoic acid(0.99 g, 2.8 mmol), 2,2′-azobisisobutyronitrile (0.07 g, 0.4 mmol),acrylic acid (1.03 g, 14.3 mmol), butyl acrylate (5.74 g, 44.8 mmol) wasprepared in dioxane (10.51 g) in a 50 mL round bottom flask. This wasstirred magnetically and sparged with nitrogen for 10 minutes. The flaskwas then heated at 70° C. for 5 hrs under constant stirring. The finalcopolymer solution was 42.7% solids.

Part (b): Preparation of Thermofusable Powder Coating Particles UsingMacro RAFT Agent Prepared in Part (a) As Pigment Stabiliser.

Titanium dioxide (19.98 g) was dispersed in a solution of butyl acrylate(10.19 g, 0.08 mole), methyl methacrylate (29.99 g, 0.30 mole), macroRAFT agent (3.86 g, 0.6 mmol), by mixing. To this dispersion, ResiflowPL200A (0.81 g) was added and the dispersion was further dispersed usinga Vibra-Cell Ultrasonic Processor (Sonics and Materials, Inc.) standardprobe set to 30% amplitude for 5 minutes. After sonication, the whitedispersion was transferred to a 100 mL round bottom flask containing2,2′-azobisisobutyronitrile (0.10 g, 0.6 mmol), dodecyl thiol (0.56 g,2.8 mmol) and hydrogenated castor oil (HCO, 0.82 g) and was sealed thendeoxygenated by nitrogen sparging for 10 minutes. The flask was immersedin a temperature controlled oil bath for 1 hour at 70° C., to receive aslightly viscous white dispersion, which contained 55.1% solids. To thisdispersion, a solution of butyl acrylate (5.18 g, 40.4 mmol), methylmethacrylate (15.53 g, 0.16 moles) was added. The diluted dispersion(27.00 g) was preheated to 70° C., then mixed with2,2′-azobisisobutyronitrile (0.18 g, 1.1 mmol) in a 100 mL beaker andwas then redispersed in a preheated (90° C.) polyvinyl alcohol solution(55.20 g, 2.5%, 80,000-100,000 g/mole, 88% hydrolysed) by a overheadmixer spinning at 1250 rpm over 5 minutes. The suspension was quicklytransferred to a 100 mL round bottom flask containing sodium nitrite(0.0062 g, 0.1 mmol) which was in turn sealed and deoxygenated bynitrogen sparging for 10 minutes. The polymerisation was carried out ina temperature controlled oil bath for 7 hours at 70° C., whileconstantly stirred magnetically. At the end of the polymerisation, thelatex was filtered to remove coagulations and was centrifuged and washedsix times with distilled water to receive a wet powder containingparticles with an estimated average size of 25 microns (Carl Zeissoptical light microscope). A solution of Primid XLS52 crosslinker (0.56g) and water (2.09 g) was mixed with the wet powder and the whole samplewas let to be air dried overnight forming a dry cake which was in turnbroken up by grinding using a mortar and a pestle and was sieved using a125 micron sieve. The final product formed a hard, white film on a glassslide at 200° C. after 10 minutes.

Example 17 Polymer Coated Bismuth Vanadate Particles Using Macro RAFTCopolymers

Part (a): Preparation of a poly(butyl acrylate-co-acrylic acid)Macro-RAFT Agent Containing an Average of 100 Monomer Units per Chain ina Mole Ratio of 1:1 Using:2-{[(butylsulfanyl)carbonothioyl]sulfanyl}propanoic acid

A solution of 2-{[(butyl sulfanyl)carbonothioyl]sulfanyl}propanoic acid(0.23 g, 1 mmol), 2,2′-azobisisobutyronitrile (0.07 g, 0.4 mmol),acrylic acid (3.54 g, 49.2 mmol), butyl acrylate (6.28 g, 49.0 mmol) wasprepared in dioxane (20.02 g) in a 50 mL round bottom flask. This wasstirred magnetically and sparged with nitrogen for 10 minutes. The flaskwas then heated at 70° C. for 3 hours under constant stirring. The finalcopolymer solution was 39.1% solids.

Part (b): Poly(methyl methacrylate-co-butyl acrylate) Coating of YellowBismuth Vanadate Pigment (Irgazin Yellow 2094, Ciba Specialty Chemicals)Using Macro RAFT from Part (a) as a Stabilizer.

Yellow pigment (5.28 g) was thoroughly mixed with macro RAFT from Part(a) (5.12 g, 0.17 mmol) to achieve a viscous yellow paste. To thispaste, water (50.73 g) was added and mixed while an ammonium hydroxidesolution (28%) was added drop wise until the pH of the dispersionreached 5. The dispersion was further dispersed using a Vibra-CellUltrasonic Processor (Sonics and Materials, Inc.) standard probe at 30%amplitude for 10 minutes. During the sonication process, the dispersionwas stirred magnetically and cooled in a water bath. It was thentransferred to a 100 mL round bottom flask containing4,4′-azobis(4-cyanovaleric acid) (0.0267 g, 0.1 mmol) and wasdeoxygenated by nitrogen sparging. The whole flask was immersed in anoil bath with a temperature setting of 70° C., while a deoxygenatedmixture of butyl acrylate (1.16 g, 9.1 mmol) and methyl methacrylate(3.49 g, 34.8 mmol) was fed into the flask at 0.94 g/hr over 5 hours.After monomer addition was complete, the heating was continued foranother 13 hours after which time polymerization was found to becomplete. The final latex was yellow and stable, containing particlesabout 699 nm in diameter (HPPS, Malvern Instrument Ltd) and 17.5%solids. Transmission electron microscopy showed that the latex containedindividually encapsulated bismuth vanadate particles.

Example 18 High Solid Content Encapsulated TiO₂

Part (a): Poly(methyl methacrylate-co-butyl acrylate) Coating of TiO₂Pigment (CR828, Kerr-McGee Pigments Ltd) Using Macro RAFT from Example4, Part (a) (C4-(5 butyl acrylate-co-10 acrylic acid)) as a Stabilizerat 55% Solids.

Macro RAFT from Example 4, Part (a): (1.85 g, 0.6 mmol) was mixed withwater (17.20 g) in a 100 mL beaker and was dissolved by adjusting the pHto 7 using ammonium hydroxide (28%). To this solution, TiO₂ pigment(19.91 g) was added, mixed and was further thoroughly dispersed using aVibra-Cell Ultrasonic Processor (Sonics and Materials, Inc.) standardprobe at 30% amplitude for 10 minutes. During the sonication process,the dispersion was stirred magnetically and cooled in a water bath. Thewhite dispersion (34.60 g) was transferred to a 100 mL round bottomflask containing 4,4′-azobis(4-cyanovaleric acid) (0.027 g, 0.1 mmol)and was deoxygenated by nitrogen sparging. The whole flask was immersedin an oil bath with a temperature setting of 70° C., while adeoxygenated mixture of butyl acrylate (1.39 g, 10.9 mmol) and methylmethacrylate (3.24 g, 32.4 mmol) was fed into the flask at 0.92 g/hrover 5 hours. After monomer addition was complete, the heating wascontinued for another 16 hours after which time polymerization was foundto be complete. The latex was white and stable, containing particlesabout 389 nm in diameter (HPPS, Malvern Instruments Ltd) and 54.8%solids. Transmission electron microscopy showed that the latex containedindividually encapsulated TiO₂ particles.

Example 19 Polymer Coated TiO₂

Part (a) Preparation of 2-[(Ethoxycarbonothioyl)sulfanyl]succinic acid.

Potassium O-ethylxanthate (Aldrich, 32.00 g, 200 mmol) was added all atonce to a stirred solution of maleic acid (76.56 g, 660 mmol) in water(153 mL) in an Erlenmeyer flask, followed by more water (10 mL) to washdown the addition funnel. After an initial endotherm to produce a cloudyyellow solution, the reaction began to exotherm and formed a creamprecipitate. The reaction was stirred for 5 hours at ambienttemperature, and then acidified with 10 M hydrochloric acid (10 mL). Themixture was then heated and stirred on a hotplate until a clear yellowsolution was obtained, which was then was filtered through a plug ofcotton wool and allowed to cool to 6° C. The product was collected byvacuum filtration, washed with a little cold water and dried.Recrystallization from water (65 mL) gave pale cream granules, 23.73 g,50%, mp 147.9-149.0°.

Part (b) Preparation of poly(butyl acrylate-co-acrylic acid) Macro-RAFTAgent, in Dioxane, Containing an Average of 15 Monomer Units per Chainin a Mole Ratio of 1:2 using: 2-[(Ethoxycarbonothioyl)sulfanyl]succinicacid

A solution of 2-[(Ethoxycarbonothioyl)sulfanyl]succinic acid (0.3 g, 1.3mmol), 2,2′-azobisisobutyronitrile (0.01 g, 0.1 mmol), acrylic acid (0.9g, 12.6 mmol), butyl acrylate (0.8 g, 6.3 mmol) was prepared in dioxane(2.6 g) in a 5 mL round bottom flask. The solution was sparged withnitrogen for 1 minute while being stirred magnetically. The flask wasthen heated to and maintained at 70° C. for 2.5 hrs under constantstirring. The final copolymer solution was 43.4% solids.

Part (c): Poly(methyl methacrylate-co-butyl acrylate) Coating of TiO₂Pigment (TR92, Huntsman Corporation) Using Macro RAFT from Part (b) asStabilizer.

A solution containing macro RAFT agent (0.50 g, 0.14 mmol), water (27.2g) and ammonium hydroxide, 28-30% (0.01 g, 0.11 mmol) was prepared in a50 mL beaker. The solution was dispersed using a Vibra-Cell UltrasonicProcessor (Sonics and Materials, Inc.) standard probe at 30% amplitudefor 1 minute. The pH measured to be 7.0. To this solution, TiO₂ pigment(4.99 g) was added, mixed and again thoroughly dispersed using theVibra-Cell Ultrasonic Processor (Sonics and Materials, Inc.) standardprobe at 30% amplitude for 10 minutes. During the sonication process,the dispersion was stirred magnetically. The white dispersion wastransferred to a 50 mL round flask containing 4,4′-azobis(4-cyanovalericacid) (0.01 g, 0.04 mmol) and was deoxygenated by nitrogen sparging. Theflask was immersed in an oil bath with temperature setting at 70° C.while a deoxygenated mixture of butyl acrylate (0.67 g, 5.23 mmol) andmethyl methacrylate (1.65 g, 16.48 mmol) was fed into the flask at 0.93g/hr over one hour then decreased to 0.467 g/hr for 1.5 hrs. Theresulting latex contained particles with an average diameter of 320.4 nm(HPPS, Malvern Instruments Ltd). The latex solids was 29.4%. The finallatex was examined by transmission electro microscopy and found tocontain individually encapsulated TiO₂ particles.

Example 20 Aqueous Decorative Paint Containing TiO₂ Encapsulated withina poly(methyl methacrylate-co-butyl acrylate) Coating

Part (a): Preparation of a poly(butyl acrylate-co-acrylic acid)Macro-RAFT Agent Containing an Average of 15 Monomer Units per Chain ina Mole Ratio of 1:2 Using:2-{[(butylsulfanyl)carbonothioyl]sulfanyl}propanoic acid

A solution of 2-{[(butylsulfanyl)carbonothioyl]sulfanyl}propanoic acid(4.77 g, 20.0 mmol), 2,2′-azobisisobutyronitrile (0.164 g, 0.999 mmol),acrylic acid (14.47 g, 0.201 mol) and butyl acrylate (12.93 g, 0.101mol) was prepared in dioxane (32.32 g) in a 50 mL round bottom flask.The acrylic acid and butyl acrylate samples were used as supplied. Noeffort was made to remove inhibitor. This was stirred magnetically andsparged with nitrogen for 10 minutes. The flask was then heated to, andmaintained at 70° C. for 2.5 hrs under constant stirring. Thepreparation was repeated and the final samples combined to providesufficient material for subsequent stages of this example. The finalcopolymer solution was 48.8% solids.

Part (b): Poly(methyl methacrylate-co-butyl acrylate) Coating of TiO₂Pigment (TR92, Huntsman Corporation) Using Macro RAFT Agent from thisExample as a Stabilizer.

A solution containing macro RAFT (4.262 g, 2.66 mmol), water (116.67 g)and 25% ammonium hydroxide (0.453 g, 12.9 mmol) was prepared in a 100 mLbeaker. To this solution, TiO₂ pigment (48.62 g) was added, mixed andthoroughly dispersed using a Branson Sonifier 450 with a 2 cm probe setto 15% amplitude for 5 minutes followed by 10 minutes at 20% amplitude.During the sonication process, the dispersion was stirred magnetically.The above preparation was repeated four times to obtain sufficientmaterial and the final samples were combined. The particle size of theindividual millbase preparations were measured using a MalvernZetasizer:

Particle Size nm (Z Average) Sample 1 303.5 Sample 2 308.1 Sample 3311.4 Sample 4 316.5

The combined samples (629.10 g) were transferred to a 1000 mLthree-necked flask equipped with condenser, temperature probe andmechanical agitator, containing 4,4′-azobis(4-cyanopentanoic acid)(0.545 g, 1.72 mmol) and were deoxygenated by nitrogen sparging. Thesample was adjusted to pH 6-6.5 with 25% ammonium hydroxide solution.The whole flask was immersed in an oil bath with a temperature settingof 70° C., while a deoxygenated mixture of butyl acrylate (20.59 g,0.161 mol) and methyl methacrylate (28.42 g, 0.284 mol) was fed into theflask over 4 hours. At the end of this feed,4,4′-azobis(4-cyanopentanoic acid) (0.545 g, 1.72 mmol) was added to thereaction vessel. The solution was then heated to 80° C. and a furtherdeoxygenated mixture of butyl acrylate (92.52 g, 0.722 mol) and methylmethacrylate (127.75 g, 1.276 mol) fed into the flask over 2 hours.During this feed (½ way through) a further sample of4,4′-azobis(4-cyanopentanoic acid) (0.545 g, 1.72 mmol) was added. Aftermonomer addition was complete, the heating was continued for a further 1hour after which time polymerization was found to be complete. Afterfiltering, the latex was white and stable, containing particles about625.9 nm in diameter (Z average). The latex solids were 50.5%. The finalPigment Volume Concentration was 15.4%.

In process samples were collected during the polymerization stage andcharacterized using the Malvern Zetasizer. As expected, thepolydispersity index PDI shows a clear narrowing as the polymer formsaround the pigment and the resulting particles become more spherical.

Sample 1 Z-average = 298.8 nm; PDI = 0.143 Sample 2 Z-average = 422.2nm; PDI = 0.151 Sample 3 Z-average = 542.1 nm; PDI = 0.110 Finaldispersion Z-average = 625.9 nm; PDI = 0.080

Part (c): Waterborne Low PVC Paint Formulated Using the EncapsulatedTiO₂ Dispersion from Part (b).

A gloss paint was formulated from the aqueous polymer dispersion of part(b):

The following were added in order to a mixer, followed by stirring for 5minutes: Encapsulated TiO₂ Dispersion from part (b) (pH adjusted to 8.0,800.00 g), Foamaster III (0.90 g), Propylene glycol (12.79 g), ProxelGXL (0.72 g), Teric G9A6 (2.265 g). Texanol (17.502 g) and Coasol (7.729g) were then added separately in a pencil stream whilst stirring.Stirring then continued for 10 minutes. After being premixed in aseparate pot, propylene glycol (26.83 g) and Natrosol 250 HR (2.43 g)were added to the above mixture and stirring continued for another 60minutes. The pH of the mixture was adjusted to 9.0 with a mixture ofAmmonium Hydroxide −25% (0.010 g) and water (0.50 g). Final paintproperties were as follows:

Paint Physical Properties:

Weight Solids: 47.02

Volume Solids: 36.05

WPL: 1.208

WPL Solids: 1.575

Part (d): Preparation of a Comparative Conventional Polymer Dispersion

Several control paints were prepared for comparative purposes. In orderto prepare the control paints, an acrylic polymer dispersion with thesame polymer composition as that of the encapsulated dispersion wasprepared.

The control comparative dispersion is an anionically stabilised latexwith the composition MMA/BA/AA=56.03/42.27/1.70:

De-ionised water (1277.07 g) and Alkanate WH60 (23.00 g of a 60%solution) were charged to a reactor fitted with mechanical agitator,temperature probe and condenser. The reactor was heated to 80° C. andsodium carbonate (1.75 g), de-ionised water (32.00 g) and ammoniumpersulfate (1.50 g) were then added. The reactor was held at temperaturefor 10 minutes. The monomer emulsion was pre-prepared comprisingde-ionised water (674.95 g), Alkanate WH60 (36.00 g of a 60% solution),MMA (1285.79 g, 12.84 mol), AA (39.02 g, 0.54 mol) and BA (970.20 g,7.57 mol). The monomer emulsion was prepared by adding the water andsurfactant to a vessel fitted with a stirrer. Monomers were added inorder and the completed mixture stirred rapidly to complete theemulsion. On completion of the 10 minute hold, the initiator solutioncomprising de-ionised water (475.83 g), ammonium persulfate (9.50 g) andsodium carbonate (2.00 g) together with the monomer emulsion were fed tothe reactor over a four hour period.

Once all feeds were finished, the reactor was held at reactiontemperature for 15 minutes.

Tert-butyl perbenzoate (4.95 g) was charged to the reactor and after a10 minute hold, followed by a feed of a mixture containing de-ionisedwater (50.00 g), sodium erythorbate (2.45 g) and Alkanate WH60 (0.050 gof a 60% solution) over 45 minutes.

At the end of this feed an ammonia adjustment (25% ammonium hydroxide,20.00 g) was added and cooling started. When the temperature was lessthan 40° C., de-ionised water (20.00 g), defoamer (0.50 g) and biocide(10.00 g) were added. Once cool the latex was filtered through 90 μmsilk.

The final latex had the following characteristics:

Solids 46.4%

pH=7.3

Minimum Film Forming Temperature=20° C.

Part (e): Comparative Waterborne Low PVC Paints Formulated Using theControl Polymer Dispersion from Part (d).

Comparative paints were formulated so as to enable clear identificationof any benefits derived from encapsulation of the Titanium Dioxidepigment. Both comparative and experimental paints were specificallyformulated to low PVC (i.e. gloss paints) with no extender pigmentsadded. Comparative Paint 1 was formulated to achieve the same pigmentvolume concentration, g/L, of titanium dioxide included andapproximately the same volume solids as the paint including encapsulatedpigment. Further comparative paints (2, 3 and 4) were formulated toinclude increasingly higher proportions of titanium dioxide (decreasedpolymer:pigment ratio) to allow comparison of resultant hiding power ofthe paints. Comparative paints were prepared using the followingformulae. The pigment used in the controls was dispersed in aconventional manner in preparation of these paints.

Comparative Paint Preparation:

Com- Com- Com- Com- parative parative parative parative Example 1Example 2 Example 3 Example 4 (wt %) (wt %) (wt %) (wt %) A Water 3.2993.444 3.572 3.698 A Calgon T 0.091 0.095 0.098 0.101 B Propylene glycol1.472 1.537 1.594 1.650 B Orotan 731A 0.703 0.734 0.761 0.788 B TericG9A6 0.144 0.150 0.156 0.162 B Foamaster III 0.645 0.670 0.698 0.723 BAmmonium 0.072 0.074 0.076 0.080 hydroxide −25% C Tioxide TR92 18.17018.965 19.667 20.362 D Water 1.071 1.121 1.159 1.199 E Water 4.696 4.0573.492 2.934 E Control Polymer 60.785 60.363 59.990 59.621 Dispersion -part (d) E Teric N8 0.424 0.421 0.419 0.416 E Proxel GXL 0.083 0.0820.082 0.081 F Water 2.076 2.061 2.049 2.036 G Texanol 2.014 2.000 1.9871.975 G Coasol 0.889 0.883 0.878 0.872 H Propylene glycol 3.087 3.0663.047 3.028 H Natrosol 250 HR 0.279 0.277 0.275 0.274

Method:

A. Load water to mixer. Turn on mixer. Sprinkle Calgon T in slowly andrun for 5 minutes

B. Add in order to high speed mixer whilst stirring. Run for 5 minutes.

C. Add under high speed mixing.

D. Wash down sides and shaft. Run at high speed for 20 minutes.

E. Add water and emulsion to mixer with stirrer off. Add other itemsthen stir for 15 minutes.

F. Add millbase to mixer with stirring. Washout millbase container.

G. Add Texanol and Coasol in a pencil stream whilst stirring.

H. Premix in a separate pot. Add with stirring then stir for 60 minutes.

Adjust viscosity and pH.

Paint Physical Properties:

Comparative Comparative Comparative Comparative Example 1 Example 2Example 3 Example 4 g/L TiO₂ 218 230 240 250 P:B ratio 64 67.5 70.5 73PVC 15.4 16 16.6 17.2 Weight Solids 48.27 48.91 49.48 50.04 VolumeSolids 37.36 37.70 38.01 38.31 WPL 1.204 1.213 1.220 1.228 WPL Solids1.556 1.573 1.589 1.603

Results:

Films of the paints from Example 20(c) and Comparative Example 1(equivalent mass of titanium dioxide per litre of paint) were cast ontoLeneta black and white charts with a drawdown blade having a 175 um gapand after drying for 24 hours were measured for gloss with a Dr Langegloss meter. They were also evaluated for film appearance and visualopacity:

Example 20 (c) Comparative Example 1 Film Appearance Excellent FlowAverage Flow Very Good DOI Poor DOI Gloss 20 36 10 60 66.5 49.9 85 93.185.7 Visual Opacity (wet) 3 2 1-6 (poor-best) Visual Opacity (dry) 3 21-6 (poor-best)

From the values above, it can be seen that the measured gloss of thefilm from paint example 20(c) at all three angles is significantlyhigher. The film of this paint showed greater brilliance and distinctionof images reflected from the surface, than the comparative example.

The films were also evaluated for opacity by applying exemplified andcomparative paints at equivalent final film builds to Leneta 5DX blackand white opacity charts by means of a #032 wire-wound drawdown bar. Thereflectance of each of the films could then be measured over the blackand white substrates using a Macbeth 7000A spectrophotometer. Thereflectance data was then used to calculate opacity in terms of ContrastRatio, film build to produce a nominated colour difference and thescattering coefficient.

The method used aligns to that of ASTM D2805 “Hiding Power of Paints byReflectometry” which is designed for testing the hiding power ofpigments. The reflectance measurements over the black and whitesubstrate regions of the panels are used to calculate the Y-tristimulusvalue (or the daylight luminous reflectance factor) for each of thesubstrates. The measured contrast ratio (Yb/Yw) for films of equalthickness can then be used as a measure of hiding power of the films andin the case of equal pigment loading, a measure of the hiding efficiencyof the pigments.

Comparative Comparative Comparative Comparative Example 20(c) Example 1Example 2 Example 3 Example 4 (218 g/L) (218 g/L) (230 g/L) (240 g/L)(250 g/L) 0.98 0.97 0.98 0.99 0.99

The higher the figure, the greater the hiding power of the paint.

When evaluated visually, the film of Example 20(c) possessed excellenthiding power—the exemplified paint, at 218 g/L, displays hiding powerbetween that of comparative examples 2 and 3 at 230-240 g/L.

The dry film build opacity was also determined using an instrumentalmethod.

An even film of paint was applied to a black and white Leneta chartusing a #032 wire wound drawdown bar to a film build approaching dryhiding. Reflectance was measured over alternately black and whitesubstrates and film build measured. Using the Kubelka-Munk equations(see D Judd and G Wyszecki “Color in Business, Sacience and Industry” p427) the film thickness required to produce a nominated colourdifference can be calculated. For this test, a colour difference ofDE=0.4 was used and the film build calculated for each paint to achievethis value.

Film Build required to achieve a DE of 0.40 Example 20 (c) (218 g/L) 101Comparative Example 1 (218 g/L) 152 Comparative Example 2 (230 g/L) 122Comparative Example 3 (240 g/L) 98 Comparative Example 4 (250 g/L) 79

The lower the film build required, the greater the hiding power of thepaint. For comparison at constant pigment concentrations, thecomparative paint Example 1 requires 50% more film build than Example20(C) to produce the same colour difference. For comparison at constantfilm build, comparative Example 3 has approximately the same film buildbut 240 g/L of pigment to match the reference Example 20(C) at only 218g/L.

Scattering coefficients were measured separately by an instrumentalmethod. This function is a measure of the amount of light scattered atthe pigment/vehicle interfaces within the paint film. The scatteringcoefficient is calculated via the Kubelka-Munk theory using the samereflectance measurements as contrast ratio. The values of Rb, Rw, themeasured reflectance over White and Black substrates, W, the reflectanceof the white substrate and T the film build, are inserted in thefollowing equations:

$\begin{matrix}{{S\left( {mm}^{- 1} \right)} = {\frac{1000}{b \star T} \star {\coth^{- 1}\left( \frac{1 - {a \star R_{b}}}{b \star R_{b}} \right)}}} & \; \\{{where}\text{:}} & \; \\{a = {0.5 \star \left\lbrack {R_{w} + \frac{R_{b} + W - R_{w}}{R_{b} \star W}} \right\rbrack}} & \; \\{b = \sqrt{\left( {a^{2} - 1} \right)}} & \; \\{{\coth^{- 1}x} = {\frac{1}{2} \star {\ln \left\lbrack \frac{x + 1}{x - 1} \right\rbrack}}} & \;\end{matrix}$

For a white pigment, the S value is largely independent of wavelengthover most of the visible spectrum, so the measurements at a wavelengthof 560 nm are used here.

Variant Relative scattering Example 20 (c) (218 g/L) 111 ComparativeExample 1 (218 g/L) 100 Comparative Example 2 (230 g/L) 100 ComparativeExample 3 (240 g/L) 106 Comparative Example 4 (250 g/L) 111

For Examples at equal pigment loading of 218 g/L, the scattering ofExample 20(c) is 11% greater than Comparative Example 1. For samples atequal scatter, the Comparative Example 4 has a 15% greater pigmentloading than Example 20(c).

Further confirmation of the increased efficiency of pigment utilisationthough encapsulation of titanium dioxide by the disclosed method, wasgained through the examination of the tinting strength of the paintExample 20(c) against Comparative Example 1. In this analytical method,a standardised black tinter is blended with the white base paint at aspecified concentration. The paints are applied to Leneta 5DX cardsusing a #040 wire wound drawdown bar to achieve equivalent film build.The colour of the panel prepared from this mixture is theninstrumentally compared to that of a standard.

Example 20 (c) Comparative Example 1 Initial Tint Strength (218 g/L)(218 g/L) DL 1.31 0.21 Rub-Up 0.67 0.20

Paint Example 20(c) and Comparative Example 1 were also evaluated forhydrophilic and hydrophobic stain resistance and scrub resistance.

Stain Resistance Test:

-   -   1. Samples of the paints of interest are drawn down on a        cardboard panel (Leneta black and white chart) in vertical        strips using a 50 micron draw down bar. Also included as a        reference is comparative paint example 1. The panels are allowed        to dry for 24 hours.    -   2. A variety of stains are spread horizontally across the panel.        These include ‘hydrophilic’ stains such as red wine, coffee and        waterborne drawing markers, and ‘hydrophobic’ stains such as        crayon, pastel, lipstick and a black grease similar to hand        grease.    -   3. The stains are left in place for one hour and then a        commercial cleaning solution is used with a rag to remove as        much of the stain as possible.

The residual hydrophilic and hydrophobic staining is individually ratedfrom 0 to 3 (0=no stain, 3=severe staining) and a total of all stainsrecorded. A low final value is best.

Scrub Test:

The paint of interest is drawn down on a Leneta black plastic scrubpanel using a 175 micron doctor blade. Individual panels are used foreach paint, and the panels are allowed to dry for two days, followed by16 hours at 50 degrees. The panel is installed in a scrub machine(Gardner heavy duty wear tester) and mechanically scrubbed in two placeswith a brush in the presence of an abrasive solution. The number ofscrub cycles required to fully remove the paint film is recorded forboth brushes, and the average taken. This number is then converted to arating as detailed below:

Scrub resistance is recorded as the number of cycles for the scrubmachine to break through the paint film. This is then converted to arating as detailed below:

Number of scrubs Rating  1-200 1 201-300 2 301-400 3 401-500 4 500+ 5

Results:

Example 20 (c) Comparative Example 1 Stain resistance 5 11 Good AverageScrub Resistance 5  5

Stain Results

Red Red Blue Green Purple Total wine Coffee Marker Marker Marker MarkerGel Pen Lipstick Grease Score Example 20 0 0 2 0 0 1 1 1 0 5 (c)Comparative 0 0 2 2 0 3 2 2 0 11 Example 1 Stain Rating: 0 - No stain,1 - Slightly stained, 2 - Badly stained, 3 - Severe

The exemplified paint is more resistant to stains than the conventionalcomparison.

Films of both this paint example and comparative example 1, were appliedto metal panels and exposed to radiation in a QUV cabinet for more than1,500 hours (QUV/sec model, made by Q-Panel Co., USA, UVA 340 tube, witha cycle of 4 hrs UV@60° C./4 hrs condensation@50° C.). Gloss of thefilms was measured at regular intervals to gain an appreciate of therate of gloss loss on exposure.

QUV Exposure Results for Comparative Example 1:

Total time (hrs) Gloss 0 162 382 496 595 760 925 1,092 1,262 1,448 1,58920° 10 5.9 5.7 5.4 4.2 4.8 5.0 5.1 6.4 7.1 6.9 60° 49.9 35.3 35.9 38.135 32.1 32.1 29.7 41.3 45 43.3 85° 85.7 66.3 73.1 75.5 75.3 74.7 73.173.1 75.7 80.1 77.6

QUV Exposure Results for Example 20(c):

Total time (hrs) Gloss 0 162 382 496 595 760 925 1,092 1,262 1,448 1,58920° 36 29.9 23.2 24.2 16.1 15.8 15.9 16.4 20.9 24 21.8 60° 66.5 66.962.4 64.7 56.9 56.5 57.8 57.5 61.4 58.5 62.6 85° 93.1 91.5 90.8 93 89.688.9 90.3 90.7 92.9 90.4 92.8

Example 21 High PVC Aqueous Decorative Paint Containing TiO₂Encapsulated within a poly(methyl methacrylate-co-butyl acrylate)Coating

Part (a): Preparation of a poly(butyl acrylate-co-acrylic acid)Macro-RAFT Agent Containing an Average of 15 Monomer Units per Chain ina Mole Ratio of 1:2 Using:2-{[(butylsulfanyl)carbonothioyl]sulfanyl}propanoic acid

A solution of 2-{[(butylsulfanyl)carbonothioyl]sulfanyl}propanoic acid(4.77 g, 20 mmol), 2,2′-azobisisobutyronitrile (0.164 g, 0.999 mmol),acrylic acid (14.47 g, 0.201 mol) and butyl acrylate (12.93 g, 0.101mol) was prepared in dioxane (32.32 g) in a 50 mL round bottom flask.The acrylic acid and butyl acrylate samples were used as supplied. Noeffort was made to remove inhibitor. This was stirred magnetically andsparged with nitrogen for 10 minutes. The flask was then heated to, andmaintained at 70° C. for 2.5 hrs under constant stirring. Thepreparation was repeated and the final samples combined to providesufficient material for subsequent stages of this example. The finalcopolymer solution was 48.8% solids.

Part (b): Poly(methyl methacrylate-co-butyl acrylate) Coating of TiO₂Pigment (TR92, Huntsman Corporation) Using Macro RAFT Agent from thisExample as a Stabilizer.

A solution containing macro RAFT (2.4894 g, 1.55 mmol), water (28.81 g)and 25% ammonium hydroxide (0.2650 g) was prepared in a 100 mL beaker.To this solution, TiO₂ pigment (28.44 g) was added, mixed and thoroughlydispersed using a Branson Sonifier 450 with a 2 cm probe set to 15%amplitude for 5 minutes followed by 10 minutes at 20% amplitude. Duringthe sonication process, the dispersion was stirred magnetically andcooled in a water bath. The ultrasonification process was repeated, asstated twice, until adequate pigment dispersion was achieved. The finalcopolymer solution was 50.50% solids.

The sample (48.25 g) was transferred to a 1000 mL three-necked flaskequipped with condenser, temperature probe and mechanical agitator,containing 4,4′-azobis(4-cyanopentanoic acid) (0.069 g, 0.218 mmol) andwere deoxygenated by nitrogen sparging. The sample was adjusted to pH7.5 with 25% ammonium hydroxide solution. The whole flask was immersedin an oil bath with a temperature setting of 70° C., while adeoxygenated mixture of butyl acrylate (0.61 g, 4.76 mmol) and methylmethacrylate (0.93 g, 9.29 mmol) was fed into the flask at 0.30 ml/hourover 5 hours. After monomer addition was complete, the heating wascontinued for a further 1 hour after which time polymerization was foundto be complete. After filtering, the latex was white and stable,containing particles about 332.9 nm in diameter (Z average). The latexsolids were 59.34%. The final Pigment Volume Concentration was

74.50%.

Part (c): Waterborne Low PVC Paint Formulated Using the EncapsulatedTiO₂ Dispersion from Part (b).

A high PVC paint was formulated from the aqueous polymer dispersion ofpart (b):

Encapsulated TiO₂ Dispersion from part (b) (100.00 g), was added to amixer, with stirring. Texanol (0.680 g) and Coasol (0.160 g) were thenadded separately in a pencil stream whilst stirring. Stirring thencontinued for 10 minutes. The pH of the mixture was adjusted to 9.0 witha mixture of ammonium hydroxide −25% (0.010 g) and water (0.50 g). Finalpaint properties were as follows:

Paint Physical Properties:

Weight Solids: 54.74

Volume Solids: 27.20

WPL: 1.594

WPL Solids: 3.209

PVC: 74.46

Part (d): Preparation of a Comparative Conventional Polymer Dispersion

The control comparative dispersion is an anionically stabilised latexwith the composition MMA/BA/AA=56.03/42.27/1.70:

De-ionised water (1277.07 g) and Alkanate WH60 (23.00 g of a 60%solution) were charged to a reactor fitted with mechanical agitator,temperature probe and condenser. The reactor was heated to 80° C. andsodium carbonate (1.75 g), de-ionised water (32.00 g) and ammoniumpersulfate (1.50 g) were then added. The reactor was held at temperaturefor 10 minutes. The monomer emulsion was pre-prepared comprisingde-ionised water (674.95 g), Alkanate WH60 (36.00 g of a 60% solution),MMA (1285.79 g, 12.84 mol), AA (39.02 g, 0.54 mol) and BA (970.20 g,7.57 mol). The monomer emulsion was prepared by adding the water andsurfactant to a vessel fitted with a stirrer. Monomers were added inorder and the completed mixture stirred rapidly to complete theemulsion. On completion of the 10 minute hold, the initiator solutioncomprising de-ionised water (475.83 g), ammonium persulfate (9.50 g) andsodium carbonate (2.00 g) together with the monomer emulsion were fed tothe reactor over a four hour period.

At the end of this feed an ammonia adjustment (25% ammonium hydroxide,20.00 g) was added and cooling started. When the temperature was lessthan 40° C., de-ionised water (20.00 g), defoamer (0.50 g) and biocide(10.00 g) were added. Once cool the latex was filtered through 90 μmsilk.

The final latex had the following characteristics:

Solids 46.4%

pH=7.3

Minimum Film Forming Temperature=20° C.

Part (e): Comparative Waterborne High PVC Paint Formulated Using theControl Polymer Dispersion from Part (d).

A high PVC paint was formulated from the aqueous polymer dispersion ofpart (d).

A comparative paint was formulated so as to enable clear identificationof any benefits derived from encapsulation of the titanium dioxidepigment. The pigment used in the control comparison was dispersed in aconventional manner in preparation of the paint.

Stage Material Parts by weight A Deionised water 142.66 Propylene glycol63.631 Antifoam 27.888 Ammonium hydroxide - 25% 3.095 Orotan 731A 30.402Teric G9A6 6.253 B Tioxide TR-92 785.57 C Deionised water 100.00 DDeionised water 235.856 Latex from part (d) of this 187.310 example ETexanol 14.66 Coasol 2.35

Stage A ingredients were added in order with stirring to a suitablysized vessel. Stage B ingredients were added and then dispersed at highspeed for 20 min. The combined A and B stages were added to a separatevessel using the Stage C to wash out the dispersion vessel. Stage Dingredients were pre-mixed and added to the combined A-C with stirring,and the combination stirred for a further 20 minutes. Stage E waspre-mixed and added as a pencil stream. Final paint properties were asfollows:

Paint Physical Properties:

Weight Solids: 57.18

Volume Solids: 31.51

WPL: 1.600

WPL Solids: 2.903

PVC: 71.85

Results:

Films of the paints from Example 21(c) and the comparative example 1were cast onto Leneta black and white charts with a drawdown bladehaving a 175 um gap and after drying for 24 hours were measured forgloss with a Dr Lange gloss meter.

Example 21 (c) Comparative Example 21(e) 20 39.0 1.5 60 91.4 5.1 85 97.122.0

Stain Example 21 (c) Comparative Example 21(e) Wine 1 1 Texta (green) 32 Lipstick (red) 3 1 Grease 3 3 Stain Rating: 0 - No stain, 1 - Slightlystained, 2 - Badly stained, 3 - Severe

Example 22 Aqueous Decorative Paint Containing TiO₂ Encapsulated withina Styrene-Acrylic Polymer Coating

Part (a): Preparation of a poly(butyl acrylate-co-acrylic acid)Macro-RAFT Agent Containing an Average of 15 Monomer Units Per Chain ina Mole Ratio of 1:2 Using:2-{[(butylsulfanyl)carbonothioyl]sulfanyl}propanoic acid

A solution of 2-{[(butylsulfanyl)carbonothioyl]sulfanyl}propanoic acid(4.77 g, 20 mmol), 2,2′-azobisisobutyronitrile (0.164 g, 0.999 mmol),acrylic acid (14.47 g, 0.201 mol) and butyl acrylate (12.93 g, 0.101mol) was prepared in dioxane (32.32 g) in a 50 mL round bottom flask.The acrylic acid and butyl acrylate samples were used as supplied. Noeffort was made to remove inhibitor. This was stirred magnetically andsparged with nitrogen for 10 minutes. The flask was then heated to, andmaintained at 70° C. for 2.5 hrs under constant stirring. The finalcopolymer solution was 48.8% solids.

Part (b): Poly(methyl methacrylate-co-butylacrylate-co-styrene-co-acrylic acid-co-PLEX) Coating of TiO₂ Pigment(TR92, Huntsman Corporation) Using Macro RAFT Agent from this Example asa Stabilizer.

A solution containing macro RAFT (4.1421 g, 2.56 mmol), water (118.16 g)and 25% ammonium hydroxide (0.4404 g) was prepared in a 100 mL beaker.To this solution, TiO₂ pigment (47.26 g) was added, mixed and thoroughlydispersed using a Branson Sonifier 450 with a 2cm probe set to 15%amplitude for 5 minutes followed by 10 minutes at 20% amplitude. Duringthe sonication process, the dispersion was stirred magnetically. Theabove preparation was repeated to obtain sufficient material and thefinal samples were combined.

The combined samples (644.49 g) were transferred to a 1000 mLthree-necked flask equipped with condenser, temperature probe andmechanical agitator, containing 4,4′-azobis(4-cyanopentanoic acid)(0.543 g, 1.72 mmol) and were deoxygenated by nitrogen sparging. Thesample was adjusted to pH 6-6.5 with 25% ammonium hydroxide solution.The whole flask was immersed in an oil bath with a temperature settingof 70° C., while a deoxygenated mixture of butyl acrylate (10.70 g,83.48 mmol) and methyl methacrylate (17.67 g, 0.176 mol) was fed intothe flask over 2 hours. At the end of this feed,4,4′-azobis(4-cyanopentanoic acid) (0.543 g, 1.72 mmol) was added to thereaction vessel. The solution was then heated to 80° C. and a furtherdeoxygenated mixture of butyl acrylate (94.88 g, 0.740 mol), methylmethacrylate (102.43 g, 1.023 mol), Styrene (47.05 g, 0.452 mol), PLEX6844-0 (8.71 g) and AA (2.22 g, 30.81 mmol) fed into the flask over 3hours. During this feed (1/2 way through) a further sample of4,4′-azobis(4-cyanopentanoic acid) (0.543 g, 1.72 mmol) was added. Aftermonomer addition was complete, the heating was continued for a further 1hour after which time polymerization was found to be complete. Afterfiltering, the latex was white and stable, containing particles about654.3 nm in diameter (Z average). The latex solids were 49.39%. Thefinal Pigment Volume Concentration was 14.64%.

Part (c): Waterborne Paint Formulated Using the Encapsulated TiO₂Dispersion from Part (b).

A gloss paint was formulated from the aqueous polymer dispersion of part(b):

The following were added in order to a mixer, followed by stirring for 5minutes: Encapsulated TiO₂ Dispersion from part (b) (88.858 g),Foamaster III (0.015 g), Propylene glycol (1.340 g), Proxel GXL (0.081g), Teric N40LP (0.200 g). Texanol (6.015 g) was then added separatelyin a pencil stream whilst stirring. Stirring then continued for 10minutes. After being premixed in a separate pot, Propylene glycol (2.980g), Acrysol SCT-275 (0.181 g) and Natrosol 250 HR (0.330 g) were addedto the above mixture and stirring continued for another 60 minutes. ThepH of the mixture was adjusted to 9.0 with a mixture of AmmoniumHydroxide −25% and water. Final paint properties were as follows:

Paint Physical Properties:

Weight Solids: 44.42

Volume Solids: 33.83

WPL: 1.187

WPL Solids: 1.559

PVC: 14.65

Part (d): Preparation of a Comparative Conventional Polymer Dispersion.

The control comparative dispersion is an anionically stabilised latexwith the composition MMA/BA/STY/AA/PLEX=41.4/37.5/16.2/1.95/3

Stage Material Weight % A DI water 20.235 A Alkanate WC60(Huntsman)0.367 B DI water 0.097 B Ammonium persulphate 0.014 B Sodium carbonate0.018 C DI water 11.55 C Ammonium persulphate 0.197 C Sodium carbonate0.034 D DI water 17.625 D AlkanateWC60 (Huntsman) 0.735 D Methylmethacrylate 18.371 D Butyl acrylate 16.61 D Styrene 7.188 D Acrylicacid 0.865 D PLEX 6844-0 (Rohm) 1.331 E DI water 1.399 F TBPB * 0.033 FDI water 0.033 G Sodium erythorbate 0.049 G DI water 1.435 H TBPB *0.033 H DI water 0.033 I TBPB* 0.033 I DI water 0.033 J Ammoniumhydroxide (25%) 0.42 J DI water 0.42 K Sodium erythorbate 0.061 K DIwater 0.321 L Bevaloid 4226 (antifoam) 0.01 M DI water 0.15 M Proxel GXL(biocide) 0.1 M Acticide MBS (biocide) 0.2 TOTAL 100 TBPB = Tertiarybutyl peroxy benzoate

Method:

Load stage A to the reactor. Start N2. Heat to 80 C. During heat up,prepare premixed stages B, C & D. Stage D preparation: In a 3 L plasticbeaker using 7.5 cm cowles blade, stir at 1200 rpm for 10 minutes. At80° C., add stage B. Hold it for 10 minutes. At the end of 10 minuteshold, stop nitrogen and start feeding stage C and D. Feed stage C & Dover 4 hr at 79-81° C. At the end of the feed, wash the line with stageE. Hold for 15 minutes. Add pre mixed stage F. Simultaneously, startfeeding stage G. Feed over 45 minutes. Add pre mixed stages H and I at15 minutes interval during stage G feed. Start cooling. Add pre mixedstage J. Continue cooling. Cool to 50° C. Add stage K. Add stage L attemperature <40° C. Discharge and filter through 90 micron silk.

The final latex had the following characteristics:

Solids 45.5%

pH=7.3

Minimum Film Forming Temperature=22° C.

Part (e): Comparative Waterborne Paint Formulated Using the ControlPolymer Dispersion from Part (d).

A comparative paint was prepared using the following formula. Thepigment used in the control comparison was dispersed in a conventionalmanner in preparation of the paints.

Stage Material Weight % A Water 2.998 CalgonT 0.083 B Propylene glycol1.337 Antifoam 0.586 Ammonium hydroxide - 25% 0.065 Orotan 731A 0.639Teric N40LP 0.131 C Tioxide TR-92 16.509 D Water 3.363 E Water 1.834Latex from part (d) of this 59.959 example Teric N8 0.409 Biocide 0.082F Water 2.522 G Texanol 6.002 H Propylene glycol 2.973 Natrosol 250 HR0.329 Acrysol SCT-275 0.180

Stage A ingredients were added in order with stirring order to asuitably sized vessel. Stage B ingredients were then added withstirring. Stage C was added and then the mixture dispersed at high speedfor 20 minutes. The combined A, B and C stages were added to a separatevessel using the Stage D and Stage F to wash out the dispersion vessel.Stage E ingredients were pre-mixed and added to the combined A-C withstirring, and the combination stirred for a further 15 minutes. Stage Gwas added as a pencil stream. Stage H was pre-mixed and added withstirring. Stirring was continued for a further 60 minutes. Final paintproperties were as follows:

Paint Physical Properties:

Weight Solids: 45.50%

Volume Solids: 35.20%

WPL: 1.190

WPL Solids: 1.538

PVC: 14.65

Results:

Films of the paints from Example 22(c) and the comparative example 1were cast onto Leneta black and white charts with a drawdown bladehaving a 175 um gap and after drying for 24 hours were measured forgloss with a Dr Lange gloss meter. They were also evaluated for filmappearance:

Property Film Appearance Example 22 (c) Comparative Example GlossExcellent Flow Average Flow 20 56 37 60 80 75 85 97 94

Example 23 Reconstituted Decorative Paint Produced from Dried PigmentedLatex

Part (a): Preparation of a poly(butyl acrylate-co-acrylic acid)Macro-RAFT Agent Containing an Average of 30 Monomer Units Per Chain ina Mole Ratio of 1:2 Using2-{[(butylsulfanyl)carbonothioyl]sulfanyl}propanoic acid

A solution of 2-{[(butylsulfanyl)carbonothioyl]sulfanyl}propanoic acid(4.77 g, 20.01 mmol), 2,2′-azobisisobutyronitrile (0.164 g, 1.0 mmol),acrylic acid (14.47 g, 199.13 mmol), butyl acrylate (12.93 g, 100.023mmol) in dioxane (32.32 g) was prepared in a 50 mL round bottom flask.This was stirred magnetically and sparged with nitrogen for 10 minutes.The flask was then heated at 70° C. for 3 hrs under constant stirring.The final copolymer solution has 49.76% solids.

Part (b): Preparation of a Reconstitutable White Decorative Paint Basedon a poly(methyl methacrylate-co-butyl acrylate), Tg=52° C., Coating ofTiO₂ Particles (TR92) Using the Macro-RAFT Prepared in this Example as aStabilizer.

The macro-RAFT reagent (4.09 g, 2.54 mmol), de-ionised water (118.71 g)and a 25% solution of ammonium hydroxide in water (0.43 g) were added toa 250 ml beaker. The pH of the mixture was adjusted into the range5.5-6.0 with a small amount of additional ammonium hydroxide solution.The mixture was subjected to ultra sonication with magnetic stirringusing a Branson 450 Sonifier for 1 minute at 15% power to disperse themacro-RAFT agent. TiO₂ powder (46.75 g) was then added to the mixtureand further ultra sonication was carried out for 5 minutes at a powersetting of 15% and for 10 minutes at a power setting of 20%. The qualityof pigment dispersion was checked by measurement of average particlesize using a Malvern Zetasizer. The pigment dispersion was repeated fourtimes and the products combined to give sufficient material for thepolymerisation stage. The particle size of the four pigment dispersionswere individually characterised using a Malvern Zetasizer.

Pigment dispersion Z Average nm Polydispersity Index 1 310.6 0.132 2317.2 0.122 3 310.6 0.132 4 306.6 0.132

The four pigment dispersions (650 g) were combined in a reaction vesselcontaining:

4,4′-azobis(4-cyanopentanoic acid) (0.542 g, 1.71 mmole) and theheadspace of the reaction vessel was then purged with nitrogen for 10minutes whilst raised the temperature to 70° C. The initiator4,4′-azobis(4-cyanopentanoic acid) (0.542 g, 1.71 mmole) was added wasadded to the reaction vessel and it was held for 5 minutes. Adeoxygenated solution of butyl acrylate (9.60 g, 74.91 mmole) and methylmethacrylate (35.48 g, 354.35 mmole) was fed into the reaction vesselusing a syringe pump over 4 hours. After the feed was complete, further4,4′-azobis(4-cyanopentanoic acid) (0.542 g, 1.71 mmole) was added andthe temperature of the reaction vessel was raised to 80° C. Once thetemperature was reached a deoxygenated solution of butyl acrylate (43.15g, 336.69 mmole) and methyl methacrylate (159.45 g, 1592.62 mmole) wasfed to the reaction vessel using a syringe pump over a 2 hour period. Ata point one hour into the feed, the feed was stopped, a further portionof 4,4′-azobis(4-cyanopentanoic acid) (0.542 g, 1.71 mmole) added andthe feed recommenced for the final hour. At the end of the feed thereaction vessel was held at temperature for an additional 1 hour tocomplete the polymerisation followed by cooling and adjustment of the pHinto the range 7.5-8.5 with 25% ammonium hydroxide and finallyfiltration through 40 μm silk.

The final latex had a solids content of 48.01% and a pigment volumeconcentration of 16.2% and a final particle size of 618.2 nm andpolydispersity index of 0.076 as measured by a Malvern Zetasizer.

Part (c): Preparation of a Reconstituted Decorative Paint Based on thePigmented Latex of this Example, Tg=52° C., PVC=16.2%

A portion of the pigmented latex prepared in this example was firstconcentrated by centrifuging the latex at 7500 rpm for 10 minutes usinga Beckman LB-BOM Ultracentrifuge. The clear supernatant solution wasdecanted and the solid concentrate was dried overnight at roomtemperature. The concentrated solid material was then sufficiently dryto be easily broken up and finely divided by light mechanical agitationand was then further dried overnight at room temperature.

The white powder produced was free flowing and had a measured solidscontent of 92%.

White paints were produced from wet pigmented latex (48.01% solids) andalso from the dried powder (92% solids) according to the followingprocedure.

Reconstituted Paint

The dried white powder (92% solids), (181.46 g) was added to a mixer andthe water (168.53 g) and sodium hydroxide (0.25 g) added with stirringfor 20 minutes Propylene glycol (16.0 g) was added followed by 10minutes stirring. Tego Foamex 825 (antifoam) (0.22 g) followed by 10minutes stirring and a mixture of commercial coalescencing solvents,Coasol (4.99 g) and Texanol (14.98 g). The final paint was thickenedwith a mixture of thickeners based on Acrysol DR1 (3.1 g) and AcrysolRM-2020 NPR (3.1 g) and stirred for 1 hour to complete the paintmake-up.

Control Paint:

A control paint was produced to the above procedure except for theinitial stage where the non dried pigmented latex (40.01% solids) (350g) was added to the mixer and sodium hydroxide (0.25 g) added andstirred for 20 minutes. The remaining raw materials were then added atthe level and in a manner as for the reconstituted paint.

Paint Comparison:

The comparison of the two paints showed that the characteristics of thepigmented latex were unaffected by the centrifuging and drying steps andgave paints of equivalent characteristics.

Particle size measurements using the Malvern Zetasizer showed that thereconstituted dry powder was easily dispersed and gave particle sizeequivalent to that of the undried pigmented latex.

Z Average nm Pigmented latex (48.01% solids): 618.2 Dry powder (92%solids, reconstituted to 48% solids 639.9 during paint make-up):

The paints were applied to standard opacity panels using a drawdown barand the films airdried overnight. The films showed excellent gloss andfilm appearance.

Control Paint Reconstituted Paint Viscosity Brookfield 20,000 14,940(Spindle 2) Cone & Plate(cp) 0.75 0.78 Gloss (20°/60°/85°) 6.6/33.5/86.64.6/32.0/84.5

1. A method of polymerising monomer to form polymer at the surface ofparticulate material, said method comprising: providing a dispersion ofsaid particulate material in a continuous liquid phase, said dispersioncomprising a RAFT agent as a stabiliser for said particulate material,and said continuous liquid phase comprising one or more ethylenicallyunsaturated monomers; and polymerising said one or more ethylenicallyunsaturated monomers under the control of said RAFT agent to therebyform polymer at the surface of said particulate material.
 2. The methodaccording to claim 1, wherein the dispersion of said particulatematerial is prepared by forming a composition comprising the particulatematerial, the RAFT agent and the continuous liquid phase, and the one ormore ethylenically unsaturated monomers are then added to thecomposition and polymerised under the control of the RAFT agent tothereby form polymer at the surface of the particulate material.
 3. Themethod according to claim 1, wherein the dispersion of said particulatematerial is prepared by forming a composition comprising the particulatematerial, the RAFT agent and the one or more ethylenically unsaturatedmonomers as the continuous liquid phase, and wherein said composition isdispersed in a second continuous liquid phase and the one or moreethylenically unsaturated monomers which form the first mentionedcontinuous liquid phase are polymerised under the control of the RAFTagent to thereby form polymer at the surface of the particulatematerial.
 4. The method according to claim 2, wherein the continuousliquid phase is water.
 5. The method according to claim 3, wherein thesecond continuous liquid phase is water.
 6. A method of preparing adispersion of polymer encapsulated particulate material in a liquid,said method comprising: providing a dispersion of particulate materialin a continuous liquid phase, said dispersion comprising a RAFT agent asa stabiliser for said particulate material, and said continuous liquidphase comprising one or more ethylenically unsaturated monomers; andpolymerising said one or more ethylenically unsaturated monomers underthe control of said RAFT agent to form polymer at the surface of saidparticulate material, thereby providing said dispersion of polymerencapsulated particulate material in a liquid.
 7. The method accordingto claim 6, wherein the continuous liquid phase is water and the methodprovides an aqueous dispersion of polymer encapsulated particulatematerial.
 8. A method of preparing a polymer having particulate materialdispersed therethrough, said method comprising: providing a dispersionof said particulate material in a continuous liquid phase, saiddispersion comprising a RAFT agent as a stabiliser for said particulatematerial, and said continuous liquid phase consisting essentially of oneor more ethylenically unsaturated monomers; and polymerising said one ormore ethylenically unsaturated monomers under the control of said RAFTagent to form polymer at the surface of said particulate material,thereby providing polymer having the particulate material dispersedtherethrough.
 9. The method according to claim 8, wherein the continuousliquid phase comprising the particulate material and the RAFT agent isdispersed in a second continuous liquid phase, and wherein the one ormore ethylenically unsaturated monomers are polymerised under thecontrol of the RAFT agent to form polymer at the surface of saidparticulate material to thereby provide a dispersion in the secondcontinuous liquid phase of polymer particles having the particulatematerial dispersed therethrough.
 10. A method of preparing a paint,thermofusable powder paint, filler, adhesive, toner, liquid ink, primer,sealant, diagnostic product or therapeutic product comprising preparinga dispersion of polymer encapsulated particulate material according toclaim 6, and combining said dispersion and/or polymer with one or moreformulation components.
 11. A paint, thermofusable powder paint, filler,adhesive, toner, liquid ink, primer, sealant, diagnostic product ortherapeutic product comprising a dispersion of polymer encapsulatedparticulate material prepared in accordance with claim
 6. 12. The methodaccording to any one of claim 1, wherein the particulate material is asolid.
 13. The method according to claim 12, wherein the solid isselected from inorganic pigments, organic pigments, titanium dioxide,zinc oxide, calcium carbonate, iron oxide, silicone dioxide, bariumsulfate, carbon black, phthalocyanine blue, phtalocyanine green,quinacridone, dibromananthrone, magnetic material, waxes, bioactiveagents, and combinations thereof.
 14. The method according to any one ofclaim 1, wherein the largest dimension of the particulate material is nogreater than 10 microns.
 15. The method according to claim 14, whereinthe largest dimension of the particulate material is no greater than 1micron.
 16. Polymer encapsulated particulate material that is 100microns or less in size, said particulate material being encapsulated ina substantially uniform and continuous coating of a polymer which has atleast in part been formed under the control of a RAFT agent.
 17. Polymerencapsulated particulate material that is 100 microns or less in size,wherein the polymer which encapsulates the particulate material has atleast in part been formed under the control of a RAFT agent, and whereinthe particulate material is substantially uniformly dispersed throughoutthe polymer.
 18. A composition comprising or consisting of discreteparticles of polymer encapsulated particulate material, said particulatematerial being encapsulated in a substantially uniform and continuouscoating of a polymer which has at least in part been formed under thecontrol of a RAFT agent.
 19. A composition comprising or consisting ofdiscrete particles of polymer encapsulated particulate material, saiddiscrete particles having the particulate material substantiallyuniformly dispersed throughout the encapsulating polymer, wherein theencapsulating polymer has at least in part been formed under the controlof a RAFT agent, and wherein the discrete particles are substantiallyfree of additional dispersant for the particulate material.
 20. Thecomposition according to claim 18 which is in the form of a free flowingpowder.
 21. A paint, thermofusable powder paint, filler, adhesive,primer, toner, liquid ink, sealant, diagnostic product or therapeuticproduct comprising a composition according to claim
 18. 22. A liquiddispersion of polymer encapsulated particulate material, saidparticulate material being encapsulated in a substantially uniform andcontinuous coating of a polymer which has at least in part been formedunder the control of a RAFT agent.
 23. A liquid dispersion of polymerencapsulated particulate material, said polymer encapsulated particulatematerial having the particulate material substantially uniformlydispersed throughout the encapsulating polymer, wherein theencapsulating polymer has at least in part been formed under the controlof a RAFT agent, and wherein the polymer encapsulated particulatematerial is substantially free of additional dispersant for theparticulate material.
 24. The liquid dispersion according to claim 22,wherein the liquid is water.
 25. The method according to claim 1,wherein the RAFT agent is of general formula (4):

where each X is independently a polymerised residue of an ethylenicallyunsaturated monomer, n is an integer ranging from 0 to 100, R1 is anorganic group optionally substituted with one or more hydrophilic groupsand Z is any group that can promote sufficient reactivity of thethiocarbonyl group towards radical additional while not slowing the rateof fragmentation to the extent that there is unacceptable retardation ofpolymerisation.
 26. A method of preparing a paint, thermofusable powderpaint, filler, adhesive, toner, liquid ink, primer, sealant, diagnosticproduct or therapeutic product comprising preparing a polymer havingparticulate material dispersed therethrough according to claim 8, andcombining said dispersion and/or polymer with one or more formulationcomponents.
 27. A paint, thermofusable powder paint, filler, adhesive,toner, liquid ink, primer, sealant, diagnostic product or therapeuticproduct comprising a polymer having particulate material dispersedtherethrough prepared in accordance with claim
 8. 28. The polymerencapsulated particulate material according to claim 16, wherein theRAFT agent is of general formula (4):

where each X is independently a polymerised residue of an ethylenicallyunsaturated monomer, n is an integer ranging from 0 to 100, R1 is anorganic group optionally substituted with one or more hydrophilic groupsand Z is any group that can promote sufficient reactivity of thethiocarbonyl group towards radical additional while not slowing the rateof fragmentation to the extent that there is unacceptable retardation ofpolymerisation.
 29. The composition according to claim 18, wherein theRAFT agent is of general formula (4):

where each X is independently a polymerised residue of an ethylenicallyunsaturated monomer, n is an integer ranging from 0 to 100, R1 is anorganic group optionally substituted with one or more hydrophilic groupsand Z is any group that can promote sufficient reactivity of thethiocarbonyl group towards radical additional while not slowing the rateof fragmentation to the extent that there is unacceptable retardation ofpolymerisation.
 30. The paint, thermofusable powder paint, filler,adhesive, primer, toner, liquid ink, sealant, diagnostic product ortherapeutic product according to claim 21, wherein the RAFT agent is ofgeneral formula (4):

where each X is independently a polymerised residue of an ethylenicallyunsaturated monomer, n is an integer ranging from 0 to 100, R1 is anorganic group optionally substituted with one or more hydrophilic groupsand Z is any group that can promote sufficient reactivity of thethiocarbonyl group towards radical additional while not slowing the rateof fragmentation to the extent that there is unacceptable retardation ofpolymerisation.
 31. The liquid dispersion according to claim 22, whereinthe RAFT agent is of general formula (4):

where each X is independently a polymerised residue of an ethylenicallyunsaturated monomer, n is an integer ranging from 0 to 100, R1 is anorganic group optionally substituted with one or more hydrophilic groupsand Z is any group that can promote sufficient reactivity of thethiocarbonyl group towards radical additional while not slowing the rateof fragmentation to the extent that there is unacceptable retardation ofpolymerisation.